Tail heavy approach and Landing

[M20S Driver]

I was landing my long body Eagle in KPAO with 110lb of luggage in a 12-18 kt wind yesterday (GW2950, 55deg f temp).  As I slowed down from 90kts downwind to 75 kts over the fence, I noticed that the pitch was higher compared to the same phases of approach at the same speeds.  I have a hard time explaining this since, with a tail heavy Mooney, the tail has to generate less downforce and as a result, the wing has to generate less lift to keep the balance and the pitch should be slightly less.  I know this is an oversimplification but does anyone have any experience or scientific background with this? 

My only other explanation is a downdraft on the 1-2  miles final and base stretch which is not likely but it was a windy day as I mentioned.

[201er]

More weight requires higher angle of attack at same airspeed. Perhaps the extra 110lbs of luggage is the culprit? The aftward CG only partially offsets the added weight. Or, could you have forgotten to extend the flaps?

[M20S Driver]

13 minutes ago, 201er said:

More weight requires higher angle of attack at same airspeed. Perhaps the extra 110lbs of luggage is the culprit? The aftward CG only partially offsets the added weight. Or, could you have forgotten to extend the flaps?

This flight was at the same or lower GW of the flights I am comparing it with.  I was full flap but I will double check to make sure it does go all the way to 30 deg.  

[Guitarmaster]

It has to do with CP vs. CG. Check this out.

https://aviation.stackexchange.com/questions/19388/what-is-the-difference-between-centre-of-pressure-aerodynamic-centre-and-neutra

Sent from my XT1585 using Tapatalk

[carusoam]

What stands out is the Cg part of the discussion.

Same gross weight as previous flights, is not the same as same gross weight with 110pounds in the baggage compartment.

This is why people put things in the trunk to ease the transition to the landing atttude. 

But, SDriver is reporting that the attitude was higher in this landing, not the trim required being less for the same attitude...

I would expect the same attitude is required for...

1) same gross weight.

2) same configuration.

3) same density altitude.

4) temps reported as 55°F,   no hot day issue here...

5) how does the cross-wind controls effect the attitude?

6) Was the slip used or crab kick method?

7) yes, less inverted lift is being used by the tail to achieve the same attitude. Less induced drag is nice...

PP thoughts only, not a CFI.

Best regards,

-a-

Edited May 29, 2017 by carusoam

[N201MKTurbo]

Maybe it didn't have anything to do with the weight and everything to do with the head wind.

[M20S Driver]

33 minutes ago, carusoam said:

1) same gross weight.  (YES)

2) same configuration. (YES)

3) same density altitude.  (YES)

4) temps reported as 55°F,   no hot day issue here...  (YES)

5) how does the cross-wind controls effect the attitude? ( Minimal CRAB)

6) Was the slip used or crab kick method? (SLIP in Flare)

7) yes, less inverted lift is being used by the tail to achieve the same attitude. Less induced drag is nice...  (AGREED)

PP thoughts only, not a CFI.  (ME TOO)

 

Of course the trim setting was significantly less than the other approaches with 110 lb in the back.   I only needed minimal crab on the approach and slip was in flare...

[M20S Driver]

25 minutes ago, N201MKTurbo said:

Maybe it didn't have anything to do with the weight and everything to do with the head wind.

I was using IAS and it was the same as the other approaches.  GPS speed was about 70 kts.  Was there a down draft?  I am not sure since the power setting was in line with the usual headwind approaches and varied from 14 to 11 inches.

[LANCECASPER]

Since the extra weight in the back is going to lessen the tendency to float I'd probably carry an extra 5 knots over the fence. I've seen a few long bodies with tail strikes. As long as you have plenty of runway in this case hold off til it lands. Letting it land always works better than making it land.

[M20S Driver]

1 hour ago, Guitarmaster said:

It has to do with CP vs. CG. Check this out.

https://aviation.stackexchange.com/questions/19388/what-is-the-difference-between-centre-of-pressure-aerodynamic-centre-and-neutra

Sent from my XT1585 using Tapatalk
 

This is a good explanation for showing how the forces interact.  I was cruising 4 knots faster and used much less trim in approach  ( that's why people but load in the back to go faster and flare easier) but the pitch was higher that expected on approach....  It may have been just a downdraft that I was compensating for.

[M20S Driver]

1 minute ago, LANCECASPER said:

Since the extra weight in the back is going to lessen the tendency to float I'd probably carry an extra 5 knots over the fence. I've seen a few long bodies with tail strikes. As long as you have plenty of runway in this case hold off til it lands. Letting it land always works better than making it land.

Sorry my experience with my Eagle is the opposite.  AFT CG drops my stall speed and makes me float longer.  I may be doing something wrong!!

[StevenL757]

25 minutes ago, M20S Driver said:

I was using IAS and it was the same as the other approaches.  GPS speed was about 70 kts.  Was there a down draft?  I am not sure since the power setting was in line with the usual headwind approaches and varied from 14 to 11 inches.

Was your landing CG within limit?  With your overall weight being under landing limit, and all other things being equal as you mentioned, an excessive aft CG / out of limit CG sounds like the most plausible explanation.

Im not understanding how GPS speed plays into the discussion.  IAS on final should be your point of reference for airspeed.

[Danb]

Being a windy day, it appears you've got yourself a bit or more of wind shear, a few years ago I was approaching Myrtle Beach, landed was hit with ws, ended up with a huge flat spot the tire. I did get a wind shear alert from the tower got caught up in it anyway. A plane about 15 minutes behind me wasn't so lucky he rolled it up but no one was injured. 

[M20S Driver]

22 minutes ago, StevenL757 said:

Was your landing CG within limit?  With your overall weight being under landing limit, and all other things being equal as you mentioned, an excessive aft CG / out of limit CG sounds like the most plausible explanation.

Im not understanding how GPS speed plays into the discussion.  IAS on final should be your point of reference for airspeed.

2

Was your landing CG within limit?  (YES)

With your overall weight being under landing limit, and all other things being equal as you mentioned, an excessive aft CG / out of limit CG sounds like the most plausible explanation.  (CG was also within limits).

Im not understanding how GPS speed plays into the discussion.  IAS on final should be your point of reference for airspeed. ( I only use GPS to double check/confirm ATIS)

[carusoam]

Looking at it this way...

A Strong head wind, may diminish, as you descend on final.  It would generate lower IAS as the headwind abates.

 

Increased attitude will result in decreased IAS, and increasing descent rate.

This may seam like down draft. As the low power is not going to maintain the glideslope as the attitude is increased.

 

strong logic skills may be required to follow the

1) MP for altitude control.

2) attitude for speed control logic.

 

Windy environments make these small adjustments an additional challenge to do frequently and continuously.

 

Expect when things don't make perfect sense on final... the go-around may make a good alternative.

 

i used to use a short runway with some trees on approach. Often, a second approach would be used for better energy control to get closer to the trees without having excess speed to scrub off, on the roll-out.

The second time through the traffic pattern will firm-up the observations you have made on the first approach.

I have had the high nose up experience while in the traffic pattern.  It is what some CFIs call dragging the plane in on final... it can be done, but sure isn't the best way to do it.  This may be an effect of flying behind the power curve. 

Thanks for keeping the details in the conversation going, SDriver.

 

PP thoughts only, still not a CFI...

Best regards,

-a-

 

[thinwing]

These longbodys with their big block 540/550 s really benefit from weight in the back..your 110 in back is my default condition...than if the runway is long enough (not kpao!)my Bravo just greases itself on with approach flaps only and no weird pitch changes.

[M20S Driver]

6 minutes ago, thinwing said:

These longbodys with their big block 540/550 s really benefit from weight in the back..your 110 in back is my default condition...than if the runway is long enough (not kpao!)my Bravo just greases itself on with approach flaps only and no weird pitch changes.

Agreed...  I gained a few knots in cruise with the load in the back and the trim and flare were much easier...  I can not explain the high pitch with my limited knowledge of aerodynamics.  Perhaps it was mostly a down draft that impacted the approach pitch!!!  

[thinwing]

46 minutes ago, M20S Driver said:

Agreed...  I gained a few knots in cruise with the load in the back and the trim and flare were much easier...  I can not explain the high pitch with my limited knowledge of aerodynamics.  Perhaps it was mostly a down draft that impacted the approach pitch!!!  

Well start doing all your flying with the wife in the baggage area and see how much that improves your flying!

[zaitcev]

Remember how gliders carry water ballast. The glide ratio is the same but the speed is higher in a ballasted airplane. The Vbg moves significantly. Conversely, to maintain the same speed at higher weight requires a greater angle of attack. If you want to maintain the same pitch, you need to go faster with a heavier load.

Where this becomes inconvenient is at touchdown. The flatter and faster you come in, the greater is the hazard of porpoising (and floating). Still, our airplanes were tested at gross weights, back in the day.

Edited May 30, 2017 by zaitcev

[M20S Driver]

I think we found the smoking gun.   The flap is intermittent and did not not go to full flap setting.  

Thanks for all the inputs and shared knowledge.

On 5/29/2017 at 8:13 AM, 201er said:

More weight requires higher angle of attack at same airspeed. Perhaps the extra 110lbs of luggage is the culprit? The aftward CG only partially offsets the added weight. Or, could you have forgotten to extend the flaps?

201er:  You nailed it

Driver

[LANCECASPER]

On page four of this thread I found my flap problem and fixed it inexpensively.

[M20S Driver]

14 minutes ago, LANCECASPER said:

On page four of this thread I found my flap problem and fixed it inexpensively.

My mechanic found a sticky micro switch and replaced it.  Two other switches did not feel right and we replaced them while we had the belly open and doing a surgery

[thinwing]

So no need to stick the wife in the back?

[carusoam]

Damn flap switches...

They only seem to last 20 years?

Best regards,

-a-