Originally Posted by
FlyJSH
In a thread somewhere, there was a comment stating pilots flying large/heavy jets at high altitudes should hand-fly some to get the feel of how the aircraft handles. While I have fair experience flying a straight wing in the low flight levels, I am wondering how a swept wing handles in rarefied air. Is it akin to flying a small airplane near its service ceiling (semi-slow flight, sluggish to control inputs, unforgiving of uncoordinated flight)?
Thanks
J
When I was a new co-pilot on the KC-10 (DC-10), part of our training was high altitude handling and we had to fly a portion of a flight at cruise without the use of the AP. During UPT, I also hand flew the T-1 (Beech 400A) without the AP.
In my experience, and anyone can correct me if I say anything out to lunch, both airplanes became pitch sensitive. In the DC-10, you literally had to fingertip fly the yoke. I had to fly a KC-10 for 2 weeks without an AP. At FL420, one quick click on the trim switches caused enough pitch change that it would measure on the VVI and you could feel the nose pitch up and down ... almost like light chop turbulence.
As you get higher, your turn radius increases significantly. Also, at a given IAS speed, you could probably bank up to 45 degrees without any buffet, but in the higher altitudes, the buffet may start at 15 degrees. I have seen students who were too aggressive in a turn at high altitude, and their faster than normal rate of bank caused us to get some buffet.
In the T-1 especially, dutch roll was much more pronounced at the higher altitudes. In fact, I think the IPs would demo turning off the yaw dampers to show this effect.
Another consideration is performance. It is very easy to get yourself on the back side of the power curve, and thus, your speed may decrease as you try to hold an altitude. In my current airplane, we call these HALAs (High Altitude Loss of Airspeed). If you get on the wrong side of the power curve, a descent of 1000 FPM may not be enough to get your speed back (MD-88 HALA simulator demo). If you allow this scenario to happen, and ATC can't give you a clearance promptly, they aren't going to like you very much when you come screaming down through the altitudes looking for airspeed. Speed management becomes very important. Reference Pinnacle Airlines Flight 3701.
I hope this answers your question.