Never ever let a jetplane stall! You have to recover immediately after the first indication off a stall!
That is what you learn during the simulator training. But today, we will turn off the stall warning systems and fly the Learjet into a complete stall – and then – recover! And we will do this over and over again. After repairing the wing’s leading edges you have to perform some test flights before the plane gets released for flight operations. Bombardier Learjet sent experienced test pilot Paul McCluskey from Wichita for this job. We started the day with an detailed briefing and Paul explained what we were going to do and why. My job was to check the speed and write down when the aircraft was stalling. During the stall the pilot must be able to keep the wings leveled and prevent the plane from rolling to one side.
Configuration for the flight:
– Takeoff with approx. 16.000 lbs
– Fuel only in the wings and tip tank – no fuel in the fuselage tank
– Extra weight behind (metal plates) the cockpit to move the “Center of Gravity” forward
– Yaw Damper OFF
– Stall Warnings OFF (then Left ON, then Right ON)
Air Traffic Controllers gave us a block altitude from FL100 up to FL150 and an area “Shuttle between VOR SULZ and Intersection REUTL with right turns at REUTL and left turns over SULZ. Call me when you’re finished”
We started with a “Clean Stall” without flaps and idle power. Below 120 kts Paul had to give more and more aileron input to keep the wings levelled. Counting down the numbers: 115, 14, 13, … 112 … 111 … 110 STALL! No more uplift and it feels like somebody cut the rope. Phuuuuuu Free Fall! Paul pushes elevator full forward and recovers. We repeated with stall warning ON to find out at which speed the stick shaker starts warning the pilot, but ignored the warning and let the speed drop until the pusher pushes the nose down. Good to know that the shaker starts “waking up the pilot” at 135 kts by 110 kts stall speed. The pusher activates just 1 or 2 knots before the actual stall.
In different configurations (Flaps 8, Flaps 20, Flaps 40) we repeated the stall exercises and I wrote down the numbers:
We returned to the airport, filled out all the documents and had a break. In the meantime the technician attached the “Stall Strip” to the wing. During our test flight it was just temporary glued to change its position if necessary. Second part of the test flight: Confirm the numbers and repeat all stalls.
After we finished Paul let me do a stall. Keeping the wings leveled at low speed was not that difficult and the stall itself was without rolling to one side. Nose down and the speed increased rapidly by loosing altitude. Even if we had enough speed – more than 140 knots – there was no laminar flow on the wings. Secondary Stall: I pulled but the wing stalls again because there was no uplift. “Wait and count: 21, 22, 23 – now recover” This time it worked and we got speed and uplift. “But don’t do this at home!” Paul reminded me. We sat together after the test flight and he told me many stories about accidents and crashes caused by pilot mistakes.
It was a day full of valuable experiences. You do not get such an opportunity to learn from such a professional that often. Thank you Paul and always happy landings!