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.