Monday, January 23, 2006

Lesson #7 Stalls

I wasn't able to get any flying done this past weekend, on Saturday the overcast was too low but I went out to the airport anyways because they were having an open house, talked to a few people and checked out some of the planes. On Sunday the wind was gusting to 35 - 40 kts so flying was out.

I took Monday afternoon off work so I could do my next lesson, stalls. As always Dave started off the lesson with a prebrief to go over what we'd be covering. This usually takes 20 - 30 minutes. We went over the definiton of a stall, the different types of stalls, the warning signs and most importantly, how to recover. We also went over some of the safety aspects of the lesson, HASEL checks, minimum height requirements etc.

The idea of this lesson is to identify the early symptoms of a stall and prevent them from occuring, also to teach recovery techniques if you find yourself in the middle of one. Practicing stalls at 3,000 plus feet is fun, having one happen at a few hundred feet AGL on final, while your paying attention to a handful of other things can be very serious.

Most small general aviation aircraft wings stall at an angle of attack of 16 - 17 degrees. Stalls can happen at any speed and at any attitude. As a pilot it's very important to recognize the symptoms of a imminent stall, as they are most likely to happen when your low and slow, during landings and takeoffs.

Some of the symptoms of a imminent stall is buffeting, an aerodynamic vibration caused by the airflow starting to detach from the wing surface. Another obvious symptom is of course the stall warning buzzer, which is set by the manufacturer to sound just before your the wing stalls completely.

With the prebrief done I went outside and did the external part of the preflight, she needed fuel. Since it was cold and I only had a light jacket on I went back inside to find out what was taking Dave, and to get some warmth. I found him and back outside we went, short trip to the fuel pump, and back outside again to fill her up. Dave somehow managed to break the clip off pump's ground cable during this process, so he headed back inside to let them know and I jumped into Fern to keep from freezing.

Alright, all that out of the way. Dave returned and it was time to finish the preflight, surprise... surprise... a new checklist. My previous flight instructor had a great checklist, one created with the student in mind. Somehow this checklist has vanished and Dave is trying to find or edit (not sure which) a checklist that works for him. All the checklists are basically the same, check this and confirm that, but the steps can be in a slightly different order and they can be divided up differently too. I like to get a much as possible done while still on the apron, then once we're on the runway a few final checks and then we're good to go. I'm thinking about creating my own checklist, one that works for me and doesn't change week to week. Of course if I decide to do this I'll have Dave review it and make sure there are no errors or missing items.

Preflight done, I taxi us out to the runway 21, backtrack a bit, turn us around and off we go. Takeoff was fine and I closely watch our heading to minimize our drift to the left. I let the nose get a bit too high on our climb out, Dave called me on it just as I'm about to lower it on my own. I quickly get her trimmed and make a climbing turn to the northwest, calling tower to let them know.

To start things off Dave had me put us into slow flight, which I did. He then took control and demonstrated a power off stall with a flawless recovery, I then attempted to replicate. My first stall went fine, pull the power back, hold the nose up to maintain altitude, hold it, hold it, nose is starting to get high, stall warning buzzer starts wailing, then the nose drops nice and gentle, I recover by feeding in some forward yoke while bringing power back up. Sometimes I feed in too much forward yoke, but I'm learning.

I did a few more power off stalls for practice, during one of these we had a wing drop, Dave quickly brought it back up with the rudder. Most non pilots would think that you'd bring the dropping wing back up with ailerons, turning the yoke and lowering the aileron on the dropping wing increases it's angle of attack even more, and can be a very dangerous mistake to make in a stall near the ground. You must bring the wing back up by using the rudder to yaw the plane, basically this causes the airflow to increase in speed over the dropping wing giving it more lift while at the same time you reduce the speed of airflow over the higher wing reducing its lift, this levels you out.

Next we moved on to power-on stalls, Dave started off by demonstrating one. The nose drop is much quicker compared to a power off stall. I give it a try. Stalling a plane with the engine generating a good deal of thrust it difficult to do. It requires a lot of backpressure on the yoke, I'd estimate about 40 lbs worth, and the aircraft's nose is really pointed skywards. Once the nose decides to drop, it's pretty abrupt and recovery is quite quick. Dave had me do a few for practice, as with the power off stalls I tended to input a bit too much forward yoke.

Since the cloud cover was only about 3,500 feet and we were too heavy for Dave to show me the thrills and joy of a spin, which is what we are going to be doing during our next lesson, we started back towards the airport. I called tower and made a turn to the west to line us up for a straight in approach for runway 21.

The wind was from the 180 at 7 kts, which should have pushed us to the right but we were getting pushed to left, this kept up until we got down to about 500 feet. I was feeling pretty good, I thought that I had us on a great glide scope, four white lights... the only thing is, its supposed to be two white and two red lights for a 3 degree glide. How do I forget simple stuff like this. We did start to get some red lights just as we passed the threshold...

Landing was pretty good, I did balloon slightly but I compensated just as Dave called me on it.

Another good lesson in the books.


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