Saturday, October 18, 2008

Ten Tips for the PPL Theory Test

I'm happy to report that I passed the PPL Theory Test with 95% good answers. The threshold is 70%. Big self-indulgent pat on the back to me.

The exam contains about 40 multiple-choice questions. Most questions have 4 possible answers and some questions count double. It's the usual deal: one answer is ludicrously wrong and can be discarded straight away, another one can be discarded with a little bit of thinking and you're finally left with two possible answers to choose from. That's when you really need to switch your brain into gear.

Below are some tips that I hope will help others. Keep in mind that this is about the Australian PPL Theory Test. Things are probably different in other countries, although from what I gather multiple-choice questionnaires seem to be the norm. The main differences are with the aeronautical information and the textbooks. For example, the Australian ERSA corresponds to the American A/FD (Airport/Facility Directory) , CAR (Civil Aviation Regulations) are similar to the US FAR (Federal Aviation Regulations) and so on.

1. Book your exam well in advance
Don't do what I did. I procrastinated and booked late. The only date left was two days before my PPL in-flight pre-test, with only three seats left. Lucky I got in. Success was my only option.

Depending on which assessment center you go to, there may be multiple sessions per week or only one every month or even two months. Or you may be sick on the day. Or have a personal emergency. Remember that if you fail the exam there's a minimum amount of time before you can take the exam again, and it increases with your percentage of wrong answers. If you have more wrong answers than correct ones, you may have to wait 28 days.

The exams are delivered by a private company called ASL on behalf of CASA and one option is to book with them, which is what I did. Some flying schools and aero club allow you to sit the exam on their premises, which may be cheaper but not necessarilly more convenient since you'll need to find an instructor who is allowed by CASA to invigilate the exam (not all of them can).

Just like when flying cross-country, make sure you're not caught out with no options.

2. Study as if you're instructing
If you've ever had the chance to teach in a formal setting, be it a classroom or a university lecture theater, you will have realized that you never really know a topic unless you're able to teach it and answer questions from students.

Apply the same techniques to studying PPL theory. Picture yourself explaining the different types of carb icing, or cloud types, or navigation techniques, to someone else and imagine that person asking you hard questions about it. Better still, find an actual person to bounce your knowledge (or lack thereof) off. This could be a friend, a work colleague with an interest for aviation or an understanding family member. Or team up with other PPL students in a study group. If you have a blog, blog about it. Even airline captains do it.

Diagrams are especially tricky. Sure, you can follow the oil system diagram and explain what each component does, but would you be able to draw it unaided on a blank piece of paper? If you can, you really know your stuff. If you don't, more studying won't hurt.

Remember, this is not only about passing the PPL theory test, it's also about acquiring knowledge that will hopefully stay with you for your whole life as a pilot. And who knows, it might even save your life one day.

3. Show up early (and with your logbook)
Allow yourself plenty of time to get to the examination center. This way you can get familiar with the location, find where the bathroom is, drink and eat before the exam, nicely organise your material on the table and relax before the exam starts. The last thing you want is pull into the parking lot downstairs two minutes before, run up the stairs and drop your stuff on the table with your hearth still racing and sweat across your face. Only to realise you left your wallet in the car and your flight computer fell off the bag on your way up.

It is also mandatory that you show your logbook on the day of the exam so that the examiner can check you passed the BAK (Basic Aeronautical Knowledge) exam. That requirement is written multiple times in documents you'll get from ASL. If you don't have your logbook, you won't be allowed to sit the exam, will loose your money and will need to rebook for a later date. Don't let that happen to you. I know one person it happened to.

4. Read the bloody question
More. Than. Once. Understand what the question actually says, not what you would like it to say. It's way too easy to fool yourself into thinking a question matches an answer you already know, or a question you've seen in a practice exam.

Negations, for example, can be easily overlooked if reading in a hurry: there's a difference between "which of the following animals is a bird" and "which of the following animals is not a bird".

Watch out for qualifiers such as "most likely". This is an indication that, although more than one answer are formally acceptable, one is definitely more acceptable than the others and is the only right answer to the question. To a question such as "which animal is most likely to stomp on your roof in Brisbane at night" the correct answer would be "a bloody possum".

There are no "trick" questions. If you've studied well and read the questions carefully you will pass. Studying "well" is different from studying "a lot" though. Which brings us to the next point.

5. Do plenty of practice exams.
OK, that's an easy one. Of course you'll practice beforehand, right? CASA even released a set of sample exam questions a few years ago. You won't find the exact same questions at the exam obviously, but they're very close in spirit.

PPL textbooks also have their own sets of practice exams. I practiced with Bob Tait's PPL and CPL books and it's very good training. My suspicion is that CASA contracted Bob to write some of the PPL exam questions :-)

Practice in exam conditions: time yourself and only use the documentation you will have at the exam. No cheating. Identify the questions you got wrong and also the ones you got right only by chance. This will give you a list of topics you need to study again. Only redo the practice exam after you've studied and understood the topics you got wrong.

6. Practice PPL exam at CPL level
That's less crazy than you might think but only applies if you plan to move on to CPL later because the cost of buying the seven CPL theory books is rather prohibitive ($341 new for Bob Tait's collection). If you can get your hands on pre-loved or someone else's books of course go for it. Check they're not too old though.

The idea is as follows: when you look at CPL books you realise that a large portion of the material is already covered in the PPL books. In the case of Bob Tait's series of books, some sections of the CPL books (particularly Meteorology) are an exact copy and paste of the PPL book. That's fair enough, a cloud is a cloud, there's no PPL clouds and CPL clouds. By practicing at CPL level, you build up extra knowledge and confidence that will help you achieve a good mark at the PPL exam, and get you ready for the CPL exam later. Double whammy.

Now, here's the caveat: this works well for General Knowledge, Meteorology, Navigation, Human Performance & Limitations and Aerodynamics. I would not recommend it for the two topics of Air Law and Performance since these are very different at PPL and CPL level.

7. Know the VFR Flight Guide inside-out
The exam is open book as long as the book you bring are on the approved list of aeronautical documentation: CAO, CAR, ERSA, AIP, VFG, etc. You cannot bring the textbooks obviously.

Now here's my experience: don't bother at all with CAO, CAR and AIP. They're big, heavy, expensive, and if you don't know where to look you won't find what you need, or will waste time finding it. Every question about regulations that I came across in the PPL exam could be answered straight out of the VFR Flight Guide (VFG). And when you think about it, that's what the VFG is about: extract all the aeronautical information relevant to VFR pilots and present it in a form that's easy to consume. Don't forget you can use the index at the back of the book too.

Of course you'll also need the ERSA, but you'll most likely already have one forthe navigation part of the PPL curriculum. Make sure it's current since some questions require looking up specific information about aerodromes or navaids that may change from one issue to the next.

8. Double-check every single answer
An obvious one again. What I did was keep a separate sheet of paper on which, for each question, I wrote down how I came to the answer. If the question required, say, a weight and balance calculation I would write down the entire calculation. If is was about regulations or facilities, I would write the page number in VFG or ERSA where I found the answer. Do that even for answers you are absolutely sure about.

After you've answered all questions, go through the list, re-check every single answer and double-check you didn't make any stupid mistake such as clicking the wrong answer or answering question 34 using the multiple choices of question 35. I did that and found one such mistake.

9. Stay hydrated and well-fed
The exam is three and a half hours long. Think about it as a long flight in an airplane with toilets. Don't let yourself get dehydrated or your blood sugar level fall too low, this will impair your ability to think. Don't let your bladder distract you either, pee breaks are allowed. Bring a bottle of water or energy drink and cereal bars. Take a short break when needed, have a sip and a bite to eat. 210 minutes is plenty of time for answering, double-checking and triple-checking all questions if you know your stuff. No need to rush.

As a matter of fact, students on average complete the exam in 165 minutes, which is about the amount of time it took me. Then you click the final button and wait for what seems like a long long time for the result to come back. Shane described it a lot better than I could.

10. Aim for a very high mark
The pass threshold if 70%. But you should aim much higher. Why? After you've submitted your answers the examiner will hand you a certificate saying that you passed as well as the somber-sounding Knowledge Deficiency Report (KDR). The KDR lists the sections of the PPL Syllabus curriculum that match answers you got wrong.

Kindly enough CASA on their website list the areas where students fail most often:
  • Effect of lowering flaps on performance of glide or descent.
  • Factors affecting the angle of climb.
  • Calculation of beginning and end of daylight
On the day of your final PPL test, you will have an oral examination as well as a flight test. In the oral examination the examiner will quiz you on every topic you got wrong at the theory test to make sure you've fixed your knowledge deficiencies. A high mark at the theory exam will keep the oral examination short and ensure you give a good first impression to the examiner. This is the difference between the examiner thinking this guy sounds fairly switched on and motivated and Oh God, here we go again.

That's it, I hope it helps. If you have questions just leave a comment below. Remember, by law I cannot reveal which questions I had at the exam, so don't ask. Anyway, if you've found this blog post and read that far you're probably very motivated and I'm sure you'll pass first time. Good luck!

Thursday, October 9, 2008

God's Acre at Archerfield Airport

At the main entrance of Archerfield Airport in Brisbane is a small peculiar graveyard called God's Acre. It is located on the airport grounds, right in-between the road and the greasy spoon eatery favored by local pilots for lack of any other option. And as Aviatrix remarked when describing a similar place in the US, this is not an airport with its own graveyard, but rather a graveyard with its own airport.

It would be easy to believe that this cemetery is the resting place of pilots and passengers involved in fatal accidents flying in or out of Archerfield. The dates however tell a different story. The cemetery was consecrated in 1859 with the burial of Volney Grenier who fell from a horse at the age of 16 while fox hunting on a nearby farm. Archerfield Airport opened 70 years later in 1929.

To put things in an Australian perspective, Australia was only "discovered" by Captain Cook in 1770, with the first settlement established in 1788.

A well-documented history of Archerfield airport tells us that the US 5th Air Force upgraded and used Archerfield aerodrome during WWII, most notably as a base for B17 Flying Fortress heavy bombers. The airfield received the visit of General MacArthur, whose wartime headquarters were in Brisbane, as well as Eleanor Roosevelt, wife of the then President of the United States.

There is however one aviation-related plaque in the cemetery. It is dedicated to the memory of Robert Copas and Lace Maxwell, who died in a flying accident in 1994. The airplane involved in the accident, a Tiger Moth VH-UNA, was based at Archerfield.

According to the ATSB report, the accident happened while performing a wing-walking stunt at the Luskintyre airfield in the Hunter Valley in NSW.

Because of the extra drag caused by the wing-walking frame bolted onto the wings, the pilot had developed a take-off technique that would give him a decent climb rate despite the added drag. Unfortunately, this involved climbing at a speed very close to the stalling speed of the aircraft.

According to the investigation report, the engine failed soon after take-off because of a problem with the carburetor needle. The problem had already been identified on similar airplanes in other countries, but had not resulted in an Airworthiness Directive in Australia. The pilot tried to perform a flat turn to get back to the runway by kicking the rudder. This resulted in a stall and spin which killed both occupants.

I wonder how many of the local pilots take the time to visit this place. It really is less than a couple hundred meters from many of the local flying training organisations. I'm glad I did.

Monday, October 6, 2008

Nav7: Back to Redcliffe

Before starting up in Goondiwindi for the last leg of Nav7 I didn't forget to turn the GPS logger back on, so this post will be illustrated with the actual track I flew. Hopefully this will compensate for the lack of photos. GPS tracking is the aviation equivalent of reality TV: no details will be spared, and all embarassing navigation mistakes will be exposed.

The plan was to fly from Goondiwindi (YGDI) back to Redcliffe (YRED) via Millmerran (YMMN), Toowoomba (YTWB) and the township of Esk. As can be seen below, I departed Goondiwindi on runway 22, flew a short crosswind leg, turned downwind and kept climbing for an overhead departure.

I could have made my life simpler by departing on downwind rather than overhead since my outbound track was nearly parallel to the downwind leg. Another thing I could have done better would have been to make sure the extended outbound track pointed at the airfield instead of being about one mile to the north of it.

I kept climbing to 5500ft while maintaining a heading of 033 degrees to Millmerran. The track to Millmerran as drawn on the map was actually 041, but given the forecasted westerly winds at 25 knots I had computed before the flight that the nose of the airplane had to be pointed 8 degrees left of track to compensate for the expected drift. The idea was to keep flying the planned heading and check later if I was where I expected to be or if any adjustements had to be made. In a nutshell, that's the navigation technique known as dead reckoning.

About two thirds of the way to Millmerran I could see on the left-hand side a power line oriented north-south crossing a road oriented south-west north-east. From the WAC chart I could easily tell where I was, which was good, except this was not where I was supposed to be!

I was actually about 5 miles north of the track. I had already flown 45 miles from Goondiwindi, with 20 more to go before Millmerran. Maybe the wind was not as strong as forecasted or had assumed a different direction, resulting in my heading over-correcting the expected drift and taking me further to the left of track. Or maybe I misaligned the compass and the DG. Finding why it happened was anyway secondary to fixing the problem.

That's when the navigation technique known as one-in-sixty comes in handy. It is based on the fact that being off track by 1 mile after 60 miles flown means an angular error of 1 degree. 2 miles after 60 miles mean 2 degrees, and so on. It works great, at least for small angles. From a mathematical point of view, this relies on the fact that the function tan(x) can be approximated as x for small values of x. But let's not complicate things, since the beauty of the method is that it can be done in the cockpit while flying.

It goes a little bit like this: I am off track by about 5 miles after about 45 miles flown. Let's say 50 instead of 45 because it makes calculations easier. 5 in 50 is like 6 in 60. So I was over-correcting drift by 6 degrees. If I turn right 6 degrees now, I will fly parallel to my intended track. However, if I do that I will still be 5 miles off-track. So I need another one-in-sixty calculation to determine the closing angle that will take me straight to my destination. I still have 20 miles to run till Millmerran, 5 in 20 is like 15 in 60, so if I add an extra 15 degrees to the 6 degrees found previously, this means I need to turn right 21 degrees to be on a track to Millmerran. New heading is therefore 012.

And it works, as can be seen in the picture above: after turning onto the new heading my new track was pointing at Millmerran. Near Millmerran I went a bit right of track in order to keep the aerodrome on my left, simply out of curiosity. Then I turned onto a new heading and tracked for the Toowoomba aerodrome. I used the drift correction from the one-in-sixty exercise conducted a few minutes before to compute a new heading.

I picked up the ATIS for Oakey on their VOR frequency. The sequence letter for the information was Zulu, meaning the military control zone was not active and had reverted to a CTAF. My track only clipped the CTR by a mile or so, but I would nevertheless have needed to request a clearance if it had been active. No need to upset the military. I prefer to see fighter jets and big black helicopters at airshows rather than at the end of my left wingtip.

Toowoomba is blessed with an NDB navaid, so I tuned it in and the needle on the ADF was pointing straight ahead. The ADF needle points at the navaid in relation to the airframe, not in relation to the track as is the case with VOR navaids, so one has to take drift into account. However, since I was no longer offsetting a lot of drift, the nose of the airplane was pretty much pointing where the airplane was going, and therefore the needle pointing straight ahead was good news.

I made a couple of calls on the Toowoomba CTAF to let everyone know I was intending to overfly the field at 5500ft. At this altitude I couldn't really have conflicted with traffic in the circuit, but it's good practice. The GPS logger can be cold and cruel at times, pointing mistakes that would otherwise go unnoticed, but in the present case I'm happy to report that my track took me right overhead the airfield.

After Toowoomba I tracked for Esk. Under my left wing were the Cressbrook and Perseverance Creek reservoirs that I had overflown on Nav3 six months ago on my way to Oakey. The hilly scenery was really beautiful in the low light near the end of this winter afternoon. I found Esk and confirmed it with Mount Esk, the racetrack and the red rooves of the Esk Hospital. I descended to 3500ft and once clear of the ranges kept descending to 1500ft to remain under the CTA steps of Brisbane International. 

The GPS logger got its revenge when I joined the circuit at Redcliffe. I was coming in from the west at 1500ft and my track was taking me straight to the airfield. I turned right a little so as to be on the south side of the extended centerline for runway 07/25.

The dead side at Redcliffe is always to the south because all circuits are over the water, i.e. left-hand circuits for 07 and right-hand circuits for 25. That's both for reasons of not overflying populated areas, and avoiding any controlled airspace violation. The Brisbane CTA step over the Redcliffe aerodrome is at 1500ft, and there's a 1000ft step just a couple of miles south of the field.

I knew from listening to the CTAF frequency that runway 07 was in use, which I confirmed by looking at the windsock as I was descending to circuit height over the dead side. The winds had changed since earlier in the day when I took off on 25.

I joined crosswind above the opposite end of the runway. I turned downwind a bit too early so I widened the leg a bit. This is why the track does not look anything like the nice figures in flying training books. I landed on 07, taxied out and refuelled the airplane. I cancelled SARTIME by phone then sat down a few minutes to jot down some notes about the flight so that I could blog about it later. Total flying time today 4.3 hours, at $185 an hour plus $29 for landing at Archerfield. Oops. Looking forward to being able to take passengers with me to share the cost.

So that's it. The navigation part of the PPL is now over. It's a bit of a weird feeling. Next step, PPL pre-test and then test. And hopefully many more adventures after that. And I need to blog about the CSU endorsement. And the PPL theory test. And the airshow in Singapore. And write a guest post for Plastic Pilot. Too many blog topics, not enough time.

Monday, September 29, 2008

Spot the airfield: Clermont, Queensland

Enf of August, on a Qantas flight from Brisbane to Singapore. I am sitting by the window on the right-hand side. The captain makes an announcement that the city of Emerald is visible on the left-hand side. Bummer, I chose the wrong side. A few minutes later though I look out the window and notice a town in the distance. With what looks like an aerodrome to the north-west. Given that it's only a few minutes after Emerald and we're flying north-west, identifying the town shouldn't be too hard.

The town is Clermont, about 50 nautical miles to the northwest of Emerald. Sorry for the poor quality of the photos which were taken in bright daylight and from a fair distance. The atmospheric hue together with the airplane window conspired to make it all grainy and milky. Or at least that's my excuse.

According to this article in the SMH, the town was named after the town of Clermont-Ferrand in France, the hometown of Oscar de Satgé who was a powerful local postoralist and represented Clermont at the Queensland Legislative Assembly from 1869 to 1872. There was a bit of a short-lived gold rush in Clermont in the 1860s but today it is mostly coal mining and agriculture which sustain the local economy.

The hard runway 15/33 is at the front and oriented top-left bottom-right on the picture. There's a brown gravel strip to the north oriented 01/19. The aerodrome as an NDB navaid with a short range of only 35 nautical miles.

About three hours after sighting Clermont we had already left Australia and the sun was setting over the jet engine on the right wing of the A330, just as we were aproaching the Indonesian island of Java. The rings on the engine cowling remind us that the photo was taken in the week after the end of the Beijing Olympics.

Saturday, September 27, 2008

Nav7: Things get windy in Goondiwindi

I landed at Goondiwindi at the conclusion of the second leg of Nav7 with an empty water bottle and a correlatively full bladder. Note to self: get smarter with water intake on long legs. After shutting down the engine and securing the airplane my first objective was to locate a bathroom. Any bathroom for that matter.

From a distance I thought the building in the picture below was someone's house. I was ready to knock on the door and beg for the use of those kind people's lieux d'aisance when I realised this was actually the terminal building.

The building was empty but I could still access the facilities. There was a small waiting room with retro-styled lounge chairs, a few leaflets for local businesses and attractions, and a Bible. A sign on the bathroom door was advertising local joy flights conducted by Sudholz Air Charters, a charter company based in Goondiwindi which operates a Piper Saratoga and a Cessna Crusader.

The McIntyre Aero Club is housed in the same building and a plaque reminds visitors that it is Sir Joh Bjelke-Petersen who officially opened the club house in 1991, just like he did with the Barambah District Aero Club in Wondai which I visited on Nav1 and again on Nav4.

Interestingly, at least to spelling sticklers like me, his last name is spelled Peterson here, and not Petersen as it should be. I wonder if Sir Joh noticed the typo when he unveiled the plaque in 1991. My guess is that he didn't: this was the year the former Queensland Premier faced a criminal trial for perjury in relation to a large corruption scandal known as the Fitzgerald Enquiry so it's fair to assume he had more pressing worries on his mind.

There wasn't anyone around at the aero club, but they must be a nice bunch of people, given that they organise breakfast fly-ins to coincide with the Gourmet in Gundy wine, food and art festival. And of course they have a brick barbecue on the front lawn.

I had my sandwich on the nicely flowered front deck before proceeding to the back of the building.

All three motels in town offer a courtesy pick-up service from the airport. I hope they also give free rides back to the airport in the morning.

And if you're not heading for a local motel you have a choice of two local cab companies. The Gundy Cab Co. uses a six-digit phone number that takes us back to the previous century. Someone wrote "put correct phone number here" on the other sign advertising the Cotton Country Cabs, but I don't think this would be enough: the business is actually up for sale.

The tour of the aerodrome wouldn't be complete without mentioning the weather station.

The circular device in the foreground is the evaporimeter. Wind speeds and direction are measured at the top of the pole on the right, while the white box on the left measures all other parameters such as temperature, humidity and dewpoint temperature.

I walked back to the apron to check out the only two other planes parked there: a Cessna Crusader and a Cessna 182. So with our C172 that was a bit of a Cessna family reunion.

The Crusader is a six-seat twin-engined airplane with counterrotating propellers, i.e. one propeller turns clockwise while the other turns anticlockwise. This makes the mechanical design and maintenance of the airplane harder, but on the other hand avoids having one engine labeled as the critical engine, thereby improving handling in case of failure of the critical engine.

I went back to VH-SPP to prepare everything for the next leg. The wind had picked up since I landed and turned very gusty. I was surprised because gusty winds were forecasted for aerodromes further north such as Oakey (15 knots gusting at 25) and Toowoomba (16 knots gusting 26), but not for Goondiwindi where the forecast was 14 knots with no gusts.

On the synoptic below Goondiwindi is near the top of the black arrow that says 35 knots, right in-between the cold front and the trough on the east coast of Australia. For those readers more familiar with how things work in the Northern Hemisphere, keep in mind that in the Southern Hemisphere winds rotate clockwise around a low and anti-clockwise around a high.

The wind was actually so gusty I could feel the plane rock from side to side. I was getting worried that I would not be able to take-off safely. The good thing though was that the wind was less than 30 degrees off the runway direction, so I knew I could handle the crosswind component, it's the gusts in the headwind component I was worried about: what if I rotated in a gust, lifted off and then got robbed of 10 or 15 knots of headwind? This would bring me very close to stalling speed. 

I taxied to the run-up bay, did my pre-take off checks, entered the runway and backtracked. From where I was I could see the windsock quite well. The plane was still rocking a bit from side to side with the gusts. I put ailerons into the wind, full power and kept some forward pressure on the yoke to make sure the airplane would not take-off prematurely. At 65 knots airspeed I started rotating and the airplane lifted off quickly and nicely into the blue sky for the last leg of the trip.

And apologies for the corny title. I couldn't resist.

Monday, September 15, 2008

Nav7: from Archerfield to Goondiwindi

Soon after taking off from runway 28L I left the controlled airspace of Archerfield aerodrome, on my way to Goondiwindi. This marked the start of second leg of Nav7. The first one was recounted here. The last words I heard from the tower controller were "cleared for take off 28L". No notification of leaving controlled airspace, no "frequency change approved" and no requirement to make an airborne report either. That's because Archerfield is a GAAP airport, an idiosyncrasy of the Australian airspace system. A GAAP airport is a non-radar towered airport with simplified procedures designed to catter for high-density General Aviation traffic. And there's no taxi clearance either.

I was now in Class G airspace, but only a few minutes away from entering the Class C controlled airspace of the Amberley RAAF base. Most week-ends this airspace is de-active and reverts to Class G airspace where CTAF rules apply. It's just like any other non-towered aerodrome, just with much much longer and wider runways. The airspace however can become active on very short notice. The consequences of busting controlled airspace, and especially military controlled airspace being dire, I double-checked the status.

I tried to get the status from the Amberley ATIS on the NDB frequency but I couldn't hear much of the recorded voice message over the morse code and the static. So I called Brisbane radar and requested the status of Amberley, which the controller said was de-active. Good. That meant I could track direct to Gatton at 2500ft instead of having to request a clearance and possibly being told to go the long way around the aerodrome via the westbound VFR route. 

I identified the Goodna VFR entry point for Archerfield on my left and kept my eyes out for any incoming traffic. I could already see Ipswich, the Amberley aerodrome and the Swanbank Power House. I kept listening to the CTAF frequency for Amberley and made a few position reports. There was only one other plane on the frequency, a Cessna 172 doing circuits at Amberley. I could now see the township of Marburg right ahead of me in the foothills of the Mt Grandchester range. I climbed to 4500ft and found some light turbulences, a harbinger of things to come.

I kept tracking west to Gatton, which was easy to identify thanks to Lake Clarendon to the north and the highway and the railway both running west. I turned south and started climbing to 8500ft. I had initially planned to stay at 6500ft but later decided to buy myself a bit more safety and gliding distance in the event of an engine failure. 2000ft extra mean about 3 more minutes at the descent rate obtained for the best glide airspeed of 68 knots, which in turn means about 3 extra nautical miles in the glide. Over a mountain range with peaks at 3700ft, this could make  the difference between landing in a paddock in one of the valleys below or having no other place to land than a heavily timbered area on a mountain slope. Did I mention that one of the highest peaks in this area is named Mt Mistake, at 3582ft?

Turbulences were present throughout the climb but ceased suddenly as I passed 7000ft. It must have been the altitude where the temperature inversion was sitting and prevented air heated up by contact with the ground from rising any higher. My best guess is that this was a subsidence inversion caused by the air being pushed downward in a high pressure system and warmed up by adiabatic compression before spreading out parallel to the ground. Yes, I've been reading the CPL Meteorology book recently in preparation for the PPL Theory exam. Anyway, whatever the reason, the visibility above the inversion was just amazing. I could see all the way to Clifton, about 30 nautical miles away.

I was far from any CTAF so I was listening to the area frequency, which was very quiet on this Sunday afternoon. There was a lot of static though, and I couldn't make it go away by using the squelch knob. I made sure the radio was not in the test position which bypasses the squelch. I was tempted to turn the volume down but then I couldn't hear what was being said on the frequency, which is bad airmanship. Then suddenly it dawned on me. I tried using the COM2 radio instead of COM1 and the problem disappeared.

The air coming into the cabin through the ventilation duct started to get a bit colder, reminding me of the temperature when I left home earlier that day. The Outside Air Temperature (OAT) gauge indicated only 2 degrees C. That's the LCD display in the top-left corner of the instrument panel, left from the airspeed indicator. With the rule of thumb of loosing about 2 degrees per 1000ft, this was consistent with a ground temperature of about 20 degrees.

Approaching Warwick I gave a call to the CTAF, even though at this altitude I couldn't interfere with traffic in the pattern. Better safe than sorry. Over Warwick I turned right and started tracking to the south-west and Goondiwindi via Inglewood. 

Lake Leslie appeared just a few miles to my left. I looked at my map and realised the planned track was supposed to take me right over the lake. I was offtrack to the north by a few miles. I did a one-in-sixty calculation which gave me a new heading for Inglewood. By the time I had finished the calculation and turned onto the revised heading I could already see Inglewood in the distance, more than 20 miles away. Damn visibility. Makes dead reckoning navigation too easy, as Australians like to say.

I tried not to look at the GPS at all on this nav, but I still had it on just in case. I had a quick glance. My groundspeed was 81 knots. My true airspeed was around 115 knots, so that's a headwind component of 35 knots, a lot more than the forecasted 25 knots. The problem was that fuel planning in Nav7 is critical. If I had taken off from Redcliffe with full tanks, I would have had barely enough fuel to complete the flight within the legal limits. That's why I refuelled in Archerfield, which increased my fuel margin by 11 litres, or 16 minutes in the air. Now the increased headwind was robbing me of my fuel margin. Not good.

I decided to descent to 6500ft hoping that the winds were weaker there. They indeed were, and my groundspeed increased to 97 knots, 16 knots more than what I was doing 2000ft higher. The increased groundspeed came at a price though. I had crossed the 7000ft level where turbulences had stopped on climb, and they came back with a vengeance on descent. It was very very bumpy. It was like someone was slapping the airplane from the outside. Maintaining altitude within a hundred feet of 6500ft required all my attention and I was not terribly successful at that. I decided to stay at this level anyway since I only had about 20 miles to run before starting my descent into Goondiwindi.

I found the aerodrome right where I expected it, although later than expected. Maybe I should have delayed my descent a little, which would have given me a steeper descent angle and therefore a better view of the area. The fact that the runway 04/22 was nearly parallel with my track of 247 degrees didn't help spot the runway early either.

No-one could be heard on the CTAF frequency. I overflew the runway, looked at the windsock which was favoring runway 22 with a strong crosswind from the right. I joined the circuit and made a descent crosswind landing on this sealed runway. When I turned on final I was surprised by how narrow the runway looked. I looked it up later and realised it is the exact same width as the runway I am used to at Redcliffe. Only that it is double the length, hence the optical illusion that it is narrower. I had just experienced a textbook optical illusion.

I taxied to the apron, chose a parking spot not too far from the terminal and shut down. I tiddied up the airplane only to found that my empty water bottle had halved in size since I last drank from it at 8500ft. The elevation at Goondiwindi is 714 feet, which means the atmospheric pressure is about 250 hPa higher than at 8500ft, an increase of one-third. One more practical experience that confirms what the book says. One thing I love about aviation is that science is never far if one knows where to look.

Sunday, September 14, 2008

Engine start-up sequence in the 172SP

A friend I took on a local flight recently recorded a video of the engine start-up sequence for the Cessna 172SP. It's the regular start-up sequence straight from the flight manual. The engine is a fuel-injected Lycoming IO-360-L2A.

Since this was the first flight of the day, the engine had to be primed prior to start-up. This is done by setting the mixture to full rich (pushing the red knob all the way forward) and turning the electric fuel pump on for about 6 seconds, until the needle on the fuel flow gauge comes to life and gives a stable reading.

As surprising as it may sound, a stable needle on the fuel flow gauge does not indicate a stabilized fuel flow. It indicates a stabilized pressure in the fuel lines.

The distinction between pressure and fuel flow does not matter in flight: the position of the needle on the gauge is driven by a fuel pressure sensor and the gauge is marked in gallons per hour because fuel pressure and fuel flow always go hand in hand. Someone in the Lycoming lab probably one day used a piece of equipment that directly measures fuel flow and painstakingly painted ticks on the face of a fuel pressure gauge. The final touch consisted in writing FUEL FLOW in big vertical capital letters on the right-hand side of the needle.

Things are a little different at start-up because, of course, the engine is not yet running. Fuel lines most likely contain fuel vapors and not liquid fuel because liquid fuel evaporated or dripped out since the engine was last shut down.

The role of the electric fuel pump is to push fuel down the fuel lines to the fuel manifold valve and from there to the fuel discharge nozzles, effectively filling up the lines with liquid fuel and getting rid of fuel vapors. Because fuel can only escape through the tiny holes of the discharge nozzles, pressure in the fuel lines rises and stabilizes. That's when the needle on the fuel flow gauge stops moving. The engine is ready for ignition.

Ignition needs to happen as soon as possible after priming, otherwise fuel may drip down the air intake pipe and cause a fire hazard. This is because this engine features indirect injection which delivers fuel at the intake port, i.e. upstream from the intake valve that allows the fuel/air mixture into the cylinder. The other sort of fuel injection, direct injection, delivers fuel directly into the combustion chamber of the cylinder, and is referred to as "common rail" in car marketing brochures.

Turning the ignition key makes the electric starter motor rotate the engine, which makes the magnetos deliver high-voltage electricity to the spark plugs with some help from the impulse coupling, which in turn ignites the fuel-air mixture in the cylinders.

One peculiarity of starting this fuel-injected engine is that it is done with the mixture on idle cut-off, i.e. full lean. The mixture is then quickly advanced to full rich once the cylinders start to fire. Why this is so I do not know. According to a thread I read on some time ago, fuel-injected Continental engines work the opposite, they are started with the mixture in the full rich position. Go figure. I guess that's the point where pilots should stop asking questions and just trust what the POH says.

Sunday, September 7, 2008

Instrument flying in the GFPT

The Australian PPL syllabus requires student pilots to have completed two hours of instrument flying before attempting the GFPT test. Instrument flying is when the pilot flies the airplane only by reference to the instruments inside the plane, as opposed to visual flying, when the pilot looks outside the window at the ground, the sky and the horizon to find out where he is and which way is up.

The picture above shows the instrument panel of a Cessna 152 on the ground. Since the engine is not running, no suction is available from the engine-driven vacuum pump for spinning gyroscope-driven instruments such as the artificial horizon. This is why the artificial horizon shows the airplane as being banked to the left with a nose-down attitude, although it is sitting on even ground.

Luckily for us visual flyers, light aircrafts have quite a few windows. The big one at the front with bugs squashed onto it is the windscreen. That's the one you should be looking out of most of the time when doing visual flying.

Side windows are nearly as important, especially for clearing turns and checking where the airplane is in relation to the runway when coming in to land. Just try to fly a circuit in a flight simulator without changing views and you’ll realize how hard it is without side windows, especially when turning base or final.

The great thing with most Cessna airplanes is that they have a back window, which comes in handy for checking where the runway is after take-off and correcting for drift. And if you happen to fly a C152 Aerobat such as VH-IVW, there are even two narrow elongated sky windows for orientation when performing aerobatics manoeuvres.

Instrument flying assumes there is nothing useful to see through the windows. The airplane could be in clouds, or in conditions of poor visibility such as in heavy rain, fog or smoke. The way such situations are simulated in training flights is by having the student put on the so-called IFR hood.

The hood is like a big plastic baseball cap with a long curved visor sticking out the front. It is sometimes referred to as a view limiting device, which is as accurate a description as you can get since it prevents whoever is wearing it from seeing anything outside the cockpit, while still being able to look at all the instruments on the panel. In the purely hypothetical situation where the instructor would realise at 2000 feet and halfway to the training area that the hood was left behind at the club, a sheet of paper or a folded map stuck under a regular cap does a pretty fine job too.

Going back one step, why do we train for instrument flying in the PPL, since the holder of such as licence is only allowed to fly during daytime and then only according to Visual Flight Rules, i.e. with sufficient visibility to fly by reference to the outside, and never ever into clouds? Well, precisely because of what happens when one accidentally flies into clouds.

VFR flying into IMC conditions is one of the biggest killers of general aviation pilots. Research conducted at the University of Illinois in the early 90s showed that, on average, pilots start suffering from spatial disorientation on average 178 seconds after entering IMC conditions. That’s just 2 seconds short of 3 minutes. In each case, the (simulated) airplane entered a graveyard spiral with a predictable fatal outcome. The pilots being tested only knew they participated in an experiment about instrument flying, not that it was about spatial disorientation. There's a good CASA video on the topic here. Not very coincidentally, the length of the video is 178 seconds.

The rationale for instrument flying training in the PPL is therefore to teach VFR pilots how to get out of clouds as quickly as possible using only instruments. This is why the training concentrates on making turns, climbing and descending, and does not even mention about IFR procedures.

I really enjoyed these two hours of instrument flying. It is very challenging and rewarding at the same time.

The challenge comes from the fact that one has to keep a very quick scan going across the instruments on the panel. The eyes go from one instrument to the next, always going back to the artificial horizon between any two instruments. This is easier said than done. One problem I had was with not keeping a scan that was quick enough. I would then realise there was a problem once the problem had started to develop, making it harder to fix.

Or if the instructor gave me an instruction such as “turn right to a heading of 230 and climb to 2500ft”, my scan would concentrate on the Directional Gyro and the altimeter, and would forget the Airspeed Indicator. It happened once when the instructor attracted my attention to the ASI. The airspeed was bleeding, nearing the bottom of the green arc, approaching the stall. Not good.

One thing I noticed when flying on instruments is that I used the throttle a lot more than usual, making lots of adjustments to get the rate of climb where I wanted it. This was not good, since it introduced an extra independent variable into the system, i.e. one more reason why things may go wrong. The right way to do things was to set an attitude using the artifical horizon, see how the plane reacted, then adjust again when needed.

All in all I think I did good, and instrument flying really opened my eyes to a completely new way of flying the airplane, one where the relationship between power, attitude and performance becomes a lot more obvious. Thinking about it, the variables received as input and the ones available as output are the same for human pilots under the hood and for the autopilot. Not having to fight spatial disorientation may even make the job of the autopilot easier in comparison. But what makes it special for us humans is that we get such a tremendous amount of fun out of it.

Monday, September 1, 2008

Nav7: from Redcliffe to Archerfield

Nav7 is the last solo nav before the PPL pre-test and test. Last chance to fix bad habits before it's too late. The plan was to go from Redcliffe to Archerfield and refuel there, then to Goondiwindi via Gatton, Warwick and Inglewood. The third and final leg took me back to Redcliffe via Millmerran, Toowoomba and Esk. The total time spent in the air for this trip was 4.3 hours and the airplane was VH-SPP, a Cessna 172SP. A very long flight, so I'll break up the story into three posts.

For this flight I used a PhotoTrackr device that I borrowed from my friend Christian. It's basically a GPS receiver that records GPS fixes to a flash memory that can later be read by plugging the device into a PC. It is powered by a single AA battery and requires only one button to operate. The roof hook at the back of the 172 provided a perfect hanging point for maximising the number of satellites that the device can see.

The track for the first leg starts with a take-off to the west from Redcliffe Aerodrome, then south-west to the TV Towers, south-east to the Centenary Bridge and finally joining the circuit for a full-stop landing on 28R at Archerfield at 10:45AM.

The day started a lot earlier though. When I left home it was 7AM and only 6 degrees outside. Quite cold for a Queensland winter. I drove to Redcliffe with virtually no traffic and pulled into the small shopping centre next to Bunnings for a coffee and a slice of cake. Then I walked into Subway next door.

The lady was kind enough to serve me even though the store was not open yet. She even called me "keen and early". This was the first time in my entire life that these two adjectives were used in conjunction to describe my personality. It must be one of those things flying does to you. I got a foot-long roast beef sandwich with no sauce since I know from past experience how soggy the sauce can make the bread after 3 or 4 hours spent in a plastic bag at the back of the plane.

At the club I helped push planes out of the hangar then sat down for flight planning. The weather forecast was amazingly good with not a single cloud in sight, unlimited visibility and some wind from the west thanks to a large low over Tasmania. The westerlies were expected to grow stronger and gustier in the afternoon though because of an approaching cold front. The forecasted winds at the surface were 15 knots gusting at 25 for Oakey, and 16 gusting at 26 for Toowoomba. Goondiwindi had 14 knots of wind with no gusts and a crosswind component of 7 knots.

I got Tony to double-check my flight notification form. He made sure I knew where controlled airspace was and how and where to check if I needed a clearance into it or not. And also that I had checked the crosswind component for Goondiwindi. Then he signed me out and asked that I rang the club from Goondiwindi to let everyone know I had landed safely.

I took some time to pre-flight the airplane and prepare the cabin for the long flight. I made sure everything was within reach of my seat, including water, spare pencils and flight computer. I took off on 25, kept flying the runway heading then tracked for the township of Samford at 1500ft. As soon as I had a bit of time I tuned and wrote down the ATIS for Archerfield.

After Samford I started flying south, overflew the Enoggera Reservoir and made my inbound call for Archerfield abeam the TV Towers. Then I tracked 153 degrees for the Centenary Bridge. The bridge is sitting very low on the water and is hidden from view by a curtain of trees, which means it only becomes visible when one is practically over it.

Archer Tower asked me to join downwind for 28R. As I reported downwind tower informed me I was number 4 in the circuit and that I should widen my downwind leg. I reported sighting the plane in front of me and widened the circuit a bit. Then a few second later I saw another plane, a lot more to my left, and a lot closer than the previous one I had spotted. This was actually the plane I was expected to follow, not the previous one... Oops... This time around I really widened downwind, doubling the distance between me and the runway. In hindsight, I should have made sure I sighted all three airplanes ahead of me in the circuit when I was told I was number 4, not just the airplane I thought was the one prior to me in the sequence.

I landed on 28R and exited via the second taxiway. Then I taxied to the transient parking area in front of the terminal and called the refuel truck on the radio. He showed up a few minutes later and I asked him to fill up the tanks to the top. He noticed the name of the Redcliffe Aero Club etched onto the BP fuel swipe card and asked if I was on my way to Goondiwindi. I guess I'm not the first student pilot to stop at Archerfield for refuel on Nav7. He added 130 litres, which brought the tanks to their combined maximum of 201 litres.

After he left I checked fuel level and all fuel drains and did a quick walk around the airplane to make sure everything was still fine. I taxied to the grass run-up bay for 28L, making sure no plane was on final for 28R when crossing at the back of 28R on taxiway A9. After run-up checks I made sure everything was ready for take-off before calling ready, not like that time at Gold Coast when I forgot to switch the transponder on. ATIS had not changed, strobes, nav lights, transponder, DG and compass aligned, mixture on full rich, flaps up. I called ready for take-off at the holding point and was cleared for take-off and a departure to the west.

Next stop Goondiwindi. 171 nautical miles to cover with strong headwinds. Estimated duration of the leg one hour and fifty-two minutes. Average ground speed about 90 knots. That'll give us plenty of time to admire South-East Queensland unfold below us.

Sunday, August 31, 2008

The tiger, the chicken and the Russian lady

I try to always have my camera with me when I come near an airport. Good blogging material may pop out of nowhere and be gone in an instant. A few weeks ago I was at Redcliffe aerodrome for my Nav7 briefing and my photographic obsession was rewarded with a visiting Yak-18T VH-KGU parked right in front of the Redcliffe Aero Club clubhouse.

No-one could be seen near or inside the aircraft, except for the guard tiger crouched over the right-hand seat. I walked around, took pictures and wondered at many of the peculiar features of this airplane.

The Yak-18 is a full-aerobatic trainer designed right after WWII ended. Remarkably, it is still in production today, although the later models are quite different from the earlier ones. The distinctive shape of the canopy of earlier two-seat tandem models make them easily distinguishable from the later Yak-18T and its four seats in a side-by-side arrangement. This model was designed as a trainer for Aeroflot pilots and production began in 1972.

It is painted in the so-called Yellow 44 Lilya Litvak livery, after the Yak-1B airplane flown by Russian WWII hero Lilya Litvak, one of the first female fighter pilots. The legend (or, perhaps more accurately, Soviet propaganda) has it that she had painted a white lilly on the fuselage of her airplane, which earned her the nickname "The White Rose of Stalingrad", probably from male fighter pilots who couldn't tell the difference between a rose and a lilly. According to IMDB, there's a movie currently in production about Lilya Litvak's life, to be released in 2010.

On the left wing is a half-meter long heated pitot tube, with an unusual pitot tube cover in the shape of a happy-looking rubber chicken.

The engine is the M-14P, a very reliable 9-cylinder radial engine that delivers 360 HP. It uses 45 litres of fuel an hour for a cruise speed of about 130 knots and a maximum take-off weight of 1503 kg. This is quite remarkable when compared to a more modern GA aircraft from the other side of the now defunct iron curtain, such as the Cessna 172SP. The cruise speed and fuel consumption are comparable, but the Yak-18T can carry nearly 350 kg more, is fully aerobatic, and costs a lot less to buy! Granted, the Yak-18T goes through half a litre of oil an hour, but that's part of the charm of radial engines.

And just like with most radial engines, the cylinder that ends up head-down after the engine is stopped has a tendency to leak oil. Which I think is the reason for the plastic Coke bottle at the end of the pipe. I'm not quite sure the Soviet Union officials would have approved of the use of such a blatant symbol of American Imperialism on one of their iconic flying machines though.

Looking up information on, I came across this page with a lot of practical information about the M-14P, including a discussion of the hydraulic lock problem, i.e. what happens when you start a radial engine that has one cylinder with its combustion chamber full of oil. Hint: oil is not compressible, and Fred Abramson in the article above describes what happens as "very dramatic, with the airplane practically jumping off the ground". Not good.

The propeller is variable pitch. VH-KGU seems to have the original 2-blade propeller. Modifications are possible to fit a three-blade propeller for increased performance.

VH-KGU also appears near the top of this Web page, both in its current condition but also as how it once was in the Soviet Union before making its way to Australia.

On the leading edge of the left wing, not too far from the chicken-guarded pitot tube, is a stall warning vane. When the angle of attack increases above a certain value, the vane is pushed upwards and triggers an audible warning in the cockpit.

There's an air intake right under the engine cowling and another one near the root of the right wing. Note that the size of the doors only covers the landing gear leg. As a consequence, the wheels are still visible when retracted.

The air intake on the right wing provides cooling for the oil radiator situated inside the intake. The white lilly can be seen on the door, as well as the name of Lylia V Litvak in Cyrillic characters.

Last curiosity: a pin located on the upper side of each wing right above the landing gear acts as a visual indicator that the landing gear is down and locked. It took me a while to find this one out until I saw it mentioned in a flight-test article on the Yak-18T written by Peter March in the December 2001 issue of the UK Pilot magazine.

So that's all I had to say about the Yak-18T. Great plane to walk around, great plane to blog about. A lot of what I know now about the Yak-18T I wouldn't have bothered looking up if it wasn't for writing this blog entry, so once again blogging is really a two-way street.

One thing that still bothers me though is that from the figures I've come across a Yak-18T could be cheaper to own and operate than, say a Cessna 182, for a comparable cruise speed and better payload. Either there's something I'm missing or there is actually an attractive and exotic alternative to the ubiquitous Cessnas and Pipers.

Not that I am in a position to even think about owning a plane. But it's nice to know that good engineering withstands the test of time.