Wheel Landing - Forward Moment during landing

[gciampa]

Hey folks, here's a query, poser, ponder:

During wheel landings I have observed what I will characterize as a forward moment, or seemingly forward moment at the point of tochdown, when I pull the power out. Is this my imagination or is there an explanation? Curious minds want to know.... The scenario is:

1. normal approach, 65kts, 30 degrees of flaps, about 8-10 IN of MP, prop full forward

2. ease into a slight flare to break the descent, lose a few knots, touchdown is typically 60kts or a tick higher

3. main wheels *gently* touch the ground and application of forward stick to keep the mains pressed on the runway (gently is the plan anyway :-) )

4. At this point, pull the last bit of power back to slow down. *This* is the point that I detect a bit of forward moment. It seems the act of pulling off the last of the power, wants to tip the plane forward just a tick.

If actions 3 & 4 are performed nearly simultaneously, the forward moment is a bit more exaggerated.

Is this my imagination, or is there some reason for the sensation?

In chatting w/ a few folks, we have conjured up that pulling power off should cause a loss of lift on the elevator at least, which would tend to lower the tail. Emperical evidence seems to suggest otherwise.

Thanks....

[Dmadd]

perhaps the weight on the wheels bends the gear legs a tad backwards (normal) which basically puts the CG further forward, which in turn causes the nose to drop/tail to rise?

DM

[DakotaHawk]

3. main wheels *gently* touch the ground

I'm still stuck on *gently*!

Seriously - If you're giving a little forward stick to "stick it" and then pulling power, maybe the lessened prop wash is reducing lift on the elevator. Remember that the elevator is an inverted wing - it lifts downward. So when the elevator loses airflow, it "drops" in the upward direction - hence you feel like you're nosing over a little.

Just another uneducated opinion...

[Ironflight]

Could be a complex aerodynamic issue - or maybe when you pull on the throttle, you are unknowingly pushing just a bit on the stick (normal reaction of forces through your body)? RV's are very sensitive to small forces....

[vic syracuse]

There's a slight possibility that your propeller blades aren't all the way to the low pitch stops, and when you pull the last bit of power off, you are getting some extra aerodynamic braking as they go to the stops. Although, Paul may have it right in that you are subconsciously moving your stick hand at the same time.

Vic

[rv8or]

This is spliting hairs but.

Is it removing the extra airflow over the tail plane which gives negative lift especially with stick back and removing some of this negative lift pitches the nose forward.

Rob

[gciampa]

Originally Posted by vic syracuse

There's a slight possibility that your propeller blades aren't all the way to the low pitch stops, and when you pull the last bit of power off, you are getting some extra aerodynamic braking as they go to the stops. Although, Paul may have it right in that you are subconsciously moving your stick hand at the same time.

Vic

He skates, he shoots, he scores!

I am nearly sure this is exactly the cause.....I have a slight over-rev condition, 100-150 RPM's during T/O and have yet to adjust the governor stop limit or stops on the prop. To temporarily keep the RPM down, I don't quite push the prop full forward for T/O (or landings), leaving about 1/8 of an inch out.

I'll change this behaviour and report the results back.

GREAT forum...

[Don Jones]

.....wouldn't additional braking action from the prop cause the nose to pitch up instead of down?