Yaw when flaring to land in a C172

[JulieFlyGal]

I was talking to an instructor friend of mine when this topic came up for discussion. He seems quite adamant, that when landing in a C172, during the flare when you bring power to idle, the aircraft will always yaw to the left as a result of a decrease in power.

I have a few hundred hours in a C172 and I've never seen this happen. Well, it may well be that I'm concentrating on keeping the attitude straight with rudder when I flare so that I don't see it happen, but can anyone confirm that the aircraft will yaw to the left upon closing the throttle and there's no rudder input by the pilot?

If it's the opposite of slipstream effect on take-off that my friend is alluding to, then wouldn't the yaw be to the right, if anything?

[the dean]

in theory you're right Julie...your instructor is mistaken...but in reality there is no noticeable yaw....unless you friend is making the approach with a VERY high power setting which is unlikely....

by the way, i'm sure its just the terminology you have used rather than a mistake on your part...but ' attitude ' is not something that is controlled by rudder...but direction is...

[punk666]

Is your friend talking about a still wind condition or not?

Remember the 4 factors that causes a left turning tendency:

Torque Reaction from Engine and Propeller
Corkscrewing Effect of the Slipstream
Gyroscopic Action of the Propeller
Asymmetric Loading of the Propeller (P Factor) when pitched up.

When flaring the aircraft the propeller is still producing thrust so P factor would cause the aircraft to yaw to the left.

I haven't noticed it before now thinking about it because I concentrate keeping it wings level and landing it :ok:

[Dan Winterland]

This smacks of the anal minutae which some instructors like to specialise in. If you can land the thing with the fuselage pointing down the runway and with no stress on the gear and tyres, who cares!

[Cows getting bigger]

I think it is more important to recognise that any corrective action required by use of rudder will require a more significant input as speed (airflow over the control surfaces) reduces.

As for the direction of yaw, why don't you check the balance ball next time you're in the flare ? :eek: (tongue in cheek, chaps)

[Whopity]

when you bring power to idle, the aircraft will always yaw to the left as a result of a decrease in power. Which way is the engine rotating? Does it yaw right when you increase power?

[Flyingmac]

In over a thousand landings in this type I've never noticed this phenomenon. I'll try one with my eyes open and see if it's true.

[Spadhampton]

Replace your left Yaw Dampener before it's too late!

I just happen to have one right here.....

(no checks please)

[homeguard]

It is more likely that the reporters visual perception - parallax is the cause.

Sat in the left hand seat: should the pilot percieve straight ahead by looking over the spinner then the nose will appear to be to the right of the centre line. If from the P2 seat the opposite will be the case. This is a very common problem and the cause of many difficulties with landings.

The pilot expects the nose to be in line with their line of vision and will subconciously yaw the nose to the left and not be aware therefore that they are themselves yawing the aircraft to the left. The pilot must learn to look straight ahead. The PA28 has the cowling hinge as a line for reference.

Another sympton is that such pilots always land to far to the left of the centre line. Such pilots love crosswinds from the left as any required crab now looks normal to them.

[b.a. Baracus]

In over a thousand landings in this type I've never noticed this phenomenon

likewise, I have never noticed this either.

[Robin400]

Any change in power will require rudder input from the pilot.
Try a high-speed descent with the throttle closed and a low-speed climb with full throttle. Aircraft with no rudder trim are set up for cruise power, so any change from cruise power setting will require pilot input.
Closing the throttle prior to landing will require input from the pilot to maintain balanced flight.

[Chuck Ellsworth]

I am following this conversation with some interest and mostly my interest is wondering why one would be carrying so much power to the landing flare that you would need rudder input to correct the yaw when you close the throttle?

[Tinstaafl]

If a C172 yaws to the *left* - requiring right rudder input - with a *decrease* in power then its engine must have parked a bit too close to a LH version at its last overhaul.

[Tmbstory]

I thought the idea in the flare was to land the aeroplane, not to see if the nose went left or right or up or down. Pilots are supposed to be able to control these actions automatically when landing on a surface.

In a 172 model, I was lucky enough to achieve more than 3000 hours on all types of surfaces, including single lane country dirt roads and claypans without getting into too much trouble. It is a good easy aeroplane to fly, my suggestion is to enjoy it.

Tmb