Lesson Seven
I am now getting quite upset as yesterday there was a significant amount of cloud about, and being quite sad I was looking forwards to some genuine IMC. But, yet again I an jinxed as we have had crystal clear blue skies this morning.
The briefing was fairly straightforwards as today we would be looking at what is in effect the emergencies area of the IMC rating. The easiest way to triple the workload of IMC flying is to lose the suction which in most aircraft powers the AI and DI. Fortunately, designers being clever people have provided enough bits that you would still be able to remain upright and could subsequently land.
Partial panel or limited panel leaves you with 5 main instruments, 3 pressure (ASI, Altimeter and VSI), one magnetic compass and the turn coordinator. Lastly you have your tacho for power settings, which in the absence of an AI become quite important.
The pressure instruments now pretty much remain as before, but due to the lack of AI, they now become the primary indicators for pitch, by using ASI to climb at a set speed and altimiter to fly level. Using them is quite simple in isolation, but putting them into your scan correctly take practice.
The magnetic compass has very little short term stability and due to magnetic dip, can be somewhat temperamental around northerly and southerly headings. Moreover, it is very hard to use in turns, and so in IMC, we tend to revert to rate 1 turns and timing the turn.
The most impressive instrument is the turn co-ordinator. This is an electrically powered rate gyro, in that it will tell you the rate of change of a particular movement. If mounted fore and aft, it whould only give you the rate of change of heading and therefore your rate of turn (as used in turn and slip indicators), but it is mounted at a 30 degree angle to the horizontal so that it also registers a rate of change of bank. This simple change means that it becomes quite sensitive and can tell you if the plane is changing heading or angle of bank. The pilot's problem is that you cannot easily differentiate between the two at a glance. If the instrument is level then you are flying straight, and your bank angle is not changing, but you could have a steady 15 degrees of bank and a bootfull of opposite rudder. Your angle of bank isn't changing and due to the out of balance flight with the rudder, neither is your heading. The instrument will indicate wings level even though they are not. The solution is quite simply to be in balanced flight at all times. If you are in balanced flight, then the only time the turn co-ordinator is level is when the wings are level, you are not turning and you are not cahnging your angle of bank.
We flew out towards Daventry and to the North and climbed to 4000' to give us some room to play. The hood went on at about 500' and I tracked quite tidily out to the Daventry VOR before turnind North. My ability and awareness seems to be getting much better as I could fly and talk and operate the plane without losing the plot. I was, as they say "Ahead of the plane". A pleasant treat before the upcoming events.
Once established at 4000' we started to look at some unusual attitudes and recovery. With the AI this was quite easy as nose high is a similar recovery to a stall, ie. full throttle, lower the nose and roll wings level. Again for nose low, the recovery is the same as for a spiral dive, power off, roll the wings level then ease out of the dive. As there was nothing dramatic, we moved quickly on and wouldn't you know it, the suction failed. How spooky, we had only just been talking about that before the flight.
Transferring my scan to the remaining instruments was fairly easy, but the concentration required was immense. Without the pitch and roll information combined I quickly found myself behind the aircraft. I could stop it turning, but every time I looked away from the altimeter, it climbed or descended by 150' and every time I concentrated on getting level, the turn co-ordiantor veered off. I could have hung wall paper more easily wiht one hand than this. And now the voice from my right wants me to fly a set heading. Surely man is not capable of such a monstrous feat of human endeavour!. Now I had had 5 minutes of intro to partial panel in my last lesson, but my subconcious had obviously thought better of retaining that knowledge. We now had a 10 minute fight where I finally beat the aircraft into submission and managed to glimpse the delights of straight and level flight on a set heading.
The next step was a timed turn. Now, the rate 1 turn is 3 degrees per second which means all of a sudden I have the overwhelming desire to fly headings that are multiples of 30. No such luck, as my ineptitude meant my first turn was 32 seconds to reach heading. Roll out and wait for the compass, and realise I am nowhere near my desired heading needing a further turn for 7 seconds. Why am I at 3700'? Never mind, maintain heading, climb back up and then we try two complete turns. I manage to get withing 20 degrees with each and personally feel quite chuffed at that. Then into unusual attitudes.
The recovery is the same as for full panel and indeed, the various nose high attitudes don't seem to cause much problem. What does take me aback is how firm you need to be in rolling level when doing the nose down attitudes. In short, depsite my fears, the previous stuff practiced in the lesson seemed to help markedly and it all went quite smoothly.
We returned back towards base using partial panel and were offered an SRA approach. Never one to say no we said yes and just as we did, the suction started to work again. Now I quite like SRA's as all I have to do is what I am told (something my wife would probably want me to do at home
). The controller was very calm and spouted huge amounts of information at me. What did make me chuckle was the request to check my gear was down. So I obliged by looking out to my left to make sure our fixed gear hadn't mysteriously vanished, but no there it was. Following the instructions had us pop out of simulated cloud pointed at the threshold of runway 23 for landing.
All told an enjoyable but hard lesson. What it has done is improved my awarness of flying in balance and my confidence in interpreting limited panel. What it has taught me is that in a real suction failure, partial panel situation I will be making as much use of assistance as I can using such things as radar vectors to ILs or SRA approaches.
Cheers
Obs cop