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Rudder-Alerion Trim

Controlling your aircraft, using the autopilot etc.

Re: Rudder-Alerion Trim

Postby tdammers » Mon Mar 23, 2020 12:27 pm

ricj7 wrote in Sun Jan 04, 2015 1:42 am:Have figured out few things but upon landing the nose still goes up. Basically to reduce the sink rate, I go higher on the throttle and also use trim to put the nose up, so upon landing there is a "nose up" scenario even very mild to moderate. Reducing the sink rate has surely helped in avoiding the "hopping" of the plane after touching the ground.

Nose-up on landing is perfectly normal; in light aircraft like a Cessna, it's not going to be very pronounced, maybe 1-2 degrees nose-up, but in an airliner at full flaps, it can be much stronger, and Concorde used to land in a fairly extreme nose-high attitude.

This is necessary for two reasons: first, you want to touch down on the sturdy main landing gear first, and then gently lower the much smaller and more fragile nosewheel. Landing on the nosewheel first ("wheelbarrowing") easily damages the nose gear, and makes it near impossible to control the aircraft in the landing roll.

And second, you want to touch down at the right airspeed.

ricj7 wrote in Sun Jan 04, 2015 1:42 am:One question: why does plane seems to be well and steady i.e. maintaining same altitude and then slowly starts to nose down and lose height. Is that something to do with wind pressure etc. outside or something needs to be taken care of inside the cockpit.

You need to constantly adjust your control inputs to keep the aircraft flying level, it doesn't do that automatically. A well-trimmed aircraft in smooth air can usually fly "hands off" for a few seconds without changing course or altitude much, but under normal circumstances, you have to either hold on to that yoke, or let the autopilot work for you.

Also, if you don't have enough engine power to maintain both airspeed and altitude, then you will lose one or the other, and loss of airspeed generally also translates to loss of altitude (eventually, you will stall the wing). So if you've trimmed everything to maintain altitude, the aircraft will lose airspeed, and once that happens, lift will decrease, the aircraft starts to sink, and then weathervaning causes the nose to drop. If you do this with an autopilot enabled, you will still lose airspeed (an autopilot can't bypass the laws of physics), but rather than losing altitude, the autopilot will keep trimming the aircraft up, until there is so little airspeed and such a steep angle of attack that the aircraft stalls.
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