pkofman

Forward slips in a Bravo

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Just curious. 

how many of you use a forward slip in a bravo or like long body model when on final.  Flaps? No flaps? Or would avoid slips altogether. 
there are times when slipping could be very handy. Just curious as to how others use it to advantage if at all

 

peter

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29 minutes ago, pkofman said:

Just curious. 

how many of you use a forward slip in a bravo or like long body model when on final.  Flaps? No flaps? Or would avoid slips altogether. 
there are times when slipping could be very handy. Just curious as to how others use it to advantage if at all

peter

I avoid them unless needed for x-wind landings under those conditions.  According to Bob Kromer (former Mooney test pilot), crosswind determination steps were tested in the TLS/Bravo using these steps...

- Crab into the wind

- Transition to forward slip over the fence

- Touch down wing low to remain over RW CL

No brakes or power were used in order to maintain straight tracking down RW CL during rollout.

Steve

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Cross controlled and long bodies have been known not to go together... with full flaps down.

Something to do with aerodynamic shadow thrown on the tail...

So the factory responded with speed brakes on all of the LBs.


so slipping to maintain centerline is one thing... (nicely described by StevenL above)

but... max cross control, to use up energy? 

Expect getting it wrong results in a tail stall that would be hard to recover from at low altitudes...

PP thoughts only, not a CFI, good ideas to share with your favorite Mooney CFI...

best regards,

-a-

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I slip my C all the time with full flaps.  I doubt very strongly that anything amiss is going to happen to a Bravo.  But why take my word for it?  Take the bird up to a safe  altitude, slow it down, deploy the gear and flaps, and put it in a slip (keep your speed up a bit, yes?).  If something bad happens recover and come tell us all about it.

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Gents,

The Long Body, full flaps, and slipping are a real phenomena...

That does not apply to the short body...

Add that to the list of +s for the short body...

Use caution with the short body with full slip/skids... easing in, and easing out...

Having the tail wag is a set-up for a different type of stall at slow air speeds... keep the nose down too...

PP thoughts only, not a CFI...

Best regards,

-a-

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What Anthony said.  I would slip my J aggressively to lose altitude and/or speed, but major sideslipping is not a recommended practice in the long body. Speed brakes are your friend.  If you’re desperate and at 140 KIAS or below, drop the gear. Forward slips for landing are of course a different animal, and entirely normal. 

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I have found my self high and fast plenty of times and have not needed to do a slip.  Speed brakes and reducing power seems to take care of it.

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51 minutes ago, steingar said:

I slip my C all the time with full flaps.  I doubt very strongly that anything amiss is going to happen to a Bravo.  But why take my word for it?  Take the bird up to a safe  altitude, slow it down, deploy the gear and flaps, and put it in a slip (keep your speed up a bit, yes?).  If something bad happens recover and come tell us all about it.

DONT DO THIS. Steinger has 0 time in a long body and is recommending you do something the most respected test pilot Bob Kromer strongly advises against. 

I dont want to have to write a letter because of this poor advice.

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Here’s what Bob Kromer wrote from http://www.donkaye.com/donkaye.com/Bob_Krommer_on_Mooney_Slips-Part_1.html

From the Mooney List December 2, 2005 by Bob Kromer.

Slipping a Mooney

During development and certification on the M20K 252 at the factory, I encountered the aerodynamic buffeting while slipping on approach as described by Dan Eldridge in his posting on slips in his M20K 231. Obviously, this gets a test pilot's attention and we began an investigation. Thought you might be interested in what we found.  For our slip tests, we flew the M20K, the M20J and the Mooney/Porsche engineering prototypes that were at the factory at the time.  This gave us a good cross section of different aircraft configurations (short/long fuselage, different pitch trim requirements on approach, etc.)  What we found was 1) All airplanes were fine above 85 KIAS in full rudder deflection forward slips, flaps up and flaps down.  2) But somewhere between 80-85 KIAS and lower, AERODYNAMIC BUFFETING FROM THE HORIZONTAL TAIL/ELEVATOR occurred in the M20K and the Mooney/Porsche airframes ALONG WITH A SLIGHT LOSS OF ELEVATOR EFFECTIVENESS AND A SLIGHT NOSE DOWN PITCHING MOMENT.  These conditions were worsened with flaps down compared to the flaps up.  Aerodynamic tufting of the horizontal tail revealed what was happening.  In the M20K and the Mooney/Porsche with their more forward CGs, almost full nose up pitch trim is required for a "hands off" approach at the target approach airspeed.  This puts the horizontal stabilizer of the Mooney tail at a high negative angle of attack (to keep the nose up).  With the horizontal tail at this high negative angle of attack and especially with flaps full down, the local airflow over the horizontal tail is getting pretty close to max alpha, the angle of attack where the tail will stall.  I want to emphasize that IN NORMAL FLYING, THERE IS PLENTY OF MARGIN - no need to worry about the tail stalling in your M20K or long body Mooney.  But start slipping the airplane at 85 KIAS and below or have a little ice on that stabilizer leading edge and those margins can get mighty thin.  Combine a slip maneuver with some pretty good yanking on the control wheel in turbulence and you might get a partial tail stall.  We did in flight test - in the M20K the result was buffeting felt in the control wheel and the slight nose down pitching moment.  So my advice from the test pilot's seat is don't go there - especially if you fly a Mooney model that requires lots of nose up pitch trim on the approach.  An aggressive  forward slip in those airplanes with the speed low and the flaps down puts the tail in an extreme airflow condition.  The airplane will warn you with buffeting and a slight pitch down, but who knows - add some ice and look out.  This is not the way to fly your Mooney.  My bottom line opinion - keep the ball near center on the approach and you're flying the Mooney design correctly and safely with the safety margins it was meant to have.

Best Regards,

Bob Kromer    

and http://www.donkaye.com/donkaye.com/Bob_Krommer_on_Mooney_Slips-Part_2.html:

From the Mooney List December 3, 2005 by Bob Kromer

SLIPPING A MOONEY

Went up to the attic last night and dug through my old flight test data sheets from my Engineering Flight Test days at the factory.  I did find the observed data for the slip tests I did.  Looked over the data.  From those test results, here is some additional information that might help answer some of the questions that have been raised:

1.  The data shows that it's the airplanes that require lots of nose up trim for landing that are the most prone to experiencing the tail buffeting condition we talked about earlier when aggressively slipping at or below 85 KIAS.  We simply could not get the M20J prototype to buffet in a full rudder sideslip at any CG and flap condition tested, down to 1.1 Vstall.  From those test results, I think it is safe to say that the Pre-J models and the J model itself will not experience any tail buffeting/partial airflow separation over the horizontal tail in an aggressive sideslip maneuver.  So the J and Pre-J models should be okay for slipping on approach.  Not comfortable, and in my humble opinion not the way to fly a high performance airplane like a Mooney, but safe.

2.  It's the K models (and variations ther3of) and the "long body" models that showed the possibility of inducing a partial horizontal tail airflow separation in an aggressive sideslip condition.  I got it in both the Mooney/Porsche and the M20K model prototypes in the landing approach configuration.  These are the airplanes that require almost full (if not full) nose up trim for a hands off, trimmed condition on final approach. (Sometime, run your pitch trim to the full nose up position on the ground and look at the negative angle of attack of the horizontal tail.  Quite impressive). It's this high negative angle of attack with full nose up trim that puts the airflow over the horizontal tail at a fairly extreme condition.

3.  Extending the flaps adds to the downwash angle over the horizontal tail, making the negative angle of attack over the horizontal tail even greater. Mooneys spend a lot of their time at or near forward CG.  As the CG moves forward the need for more nose up trim on the approach is required for trimmed flight.  So does lower airspeed.  So the worse condition for aggressive slipping in the K and up models is slow, forward CG, full flaps - just like we are when configured for landing.  Remember, it's anything that requires the need for more nose up trim that adds to the possibility of experiencing horizontal tail buffeting when aggressively slipping on the approach.      

4.  Aggressive slipping does strange things to the local airflow over the horizontal tail.  The bottom line is this - the horizontal tail will see a greater negative angle of attack in the slip maneuver.  So add an aggressive slip to the conditions noted in #3 above and you can experience the partial airflow separation over the horizontal tail and the resulting buffeting that we found in the flight tests. The Mooney is such a good design that there is no danger here - just a buffet in the control wheel from the elevator, a slight nose down pitching moment and a little loss of elevator effectiveness.  But I want to emphasize - THIS IS NO PLACE TO BE FLYING. Add a little ice to that horizontal tail leading edge or a gusty crosswind requiring heavy elevator input and look out.  That minor buffeting and airflow separation can get worse.

5.  Someone asked what would happen to an airplane if the horizontal tail completely stalled.  The answer - bad news.  A sharp nose down pitching moment and a loss of elevator control would result.  With increased airspeed as a result of the nose down pitch, the tail might start flying again and elevator effectiveness might be restored.  But we're talking a loss of aircraft control here - a pilot's worse nightmare.  How much altitude might be lost in this loss of control experience?  A guess - 2000 feet.

6.  Incidentally, ground effect helps the condition - the downwash angle over the horizontal tail is slightly reduced with the wing/flaps in ground effect.  This reduces the local negative angle of attack of the air flowing over the horizontal tail - a good thing when it comes to stalling the horizontal tail.

Again - the bottom line.  Aggressive slips in your Pre-J or J should be okay from a safety of flight viewpoint.  K models and up - margins here are thinner.  Chances are you might experience some tail buffeting in the K models and up when aggressively slipping - not a place to be.  From my flight test experience, I would avoid aggressive slips on approach in the K's and up.  The Mooney is a wonderful design, but all designs have their limits.  

I certainly don't have all the answers and would never claim to be an "expert" or tell anyone how they need to fly their airplanes, but maybe some of my engineering flight test experiences at Mooney will help you better understand your airplanes.  I've got lots of good data in my attic.  Hope to share more of it with you in the future.

Best Regards;

Bob Kromer

Edited by Deb
thinwing posted this 12/19/2015 here https://mooneyspace.com/topic/20600-can-a-really-aggressive-forward-slip-on-final-ever-produce-a-spin/page/2/
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Couldn’t agree more with the two above regarding the Bravo 

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1 hour ago, mike_elliott said:

DONT DO THIS. Steinger has 0 time in a long body and is recommending you do something the most respected test pilot Bob Kromer strongly advises against. 

I dont want to have to write a letter because of this poor advice.

Thanks Mike.. that is exactly why I asked the question. I do use my speed brakes when required  and most of the time  things work out perfectly unless Ive  been asked to stay high and  or cut to final or some other atc requested expedite maneuver,  but I do use the slip method for wind landings.. If it all looks strange on final and im hot and high im probably going around and that's my prerogative. Im not going to do something that takes me to thin edge. 

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3 hours ago, mike_elliott said:

DONT DO THIS. Steinger has 0 time in a long body and is recommending you do something the most respected test pilot Bob Kromer strongly advises against. 

I dont want to have to write a letter because of this poor advice.

Mike, you may have your “facts” and “numbers” and “test pilot knowledge” but Steingar ”feels” that slipping a long body is all right. I’m sure he did his “research” on the internet and “he knows his plane” so who are we to believe? One guy says yes, one guy says no. I guess we’ll never know...

DISCLAIMER: I’m not recommending slipping a long body. That’s stupid. It’s just intended as a commentary on our current disregard for science and scientific thinking and the fallacy of taking action based on what “someone said on the internet” without consulting a professional. Please don’t do that. And please don’t feel compelled to give advice on something you’re not qualified to do, in case someone is foolish enough to take it.

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I never said that.   What I said was a) I do it in my short body Mooney routinely and b) I would be surprised if there were major issues in a longbody and c) the OP could resolve this whole thing by taking his airplane to a safe altitude and doing the test.  If what Deb linked is correct, he can expect a bit of buffeting and a slight pitch down motion below 85 knots.  Means don't do slips below 85 knots, doesn't it?

This scientist suggested using the scientific method to resolve a question.  And I really don't see anything inherently stupid about putting a forward slip on a Mooney.  If what I've read is correct, you just want to keep your speed up when  you do it.  I always keep my speed up in a forward slip, since I don't want to get into a cross controlled stall.  You guys remind me of all the Skyhawk pilots frightened of forward slips.

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5 minutes ago, steingar said:

This scientist suggested using the scientific method to resolve a question

Its been done many times by a multitude of Mooney "scientist". The results are known. The results wont change. Scientist dont continually test to expect different results. That is the definition of something else, not science. 

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14 minutes ago, mike_elliott said:

Its been done many times by a multitude of Mooney "scientist". The results are known. The results wont change. Scientist dont continually test to expect different results. That is the definition of something else, not science. 

I suppose that means we shouldn't do stalls either.  After all, its been done by a multitude of Mooney scientists, and we all know what happens.  We probably shouldn't do any slow flight either, since lots of Mooney scientists have shown that you can stall a Mooney at low speed.

Or, you can be a good pilot, and understand what your airplane will do at the edges of its flight envelope.  We practice these things at a safe altitude so that if something does go wrong, we have room to recover.  No pilot should ever be surprised at the performance of his aircraft.

Now, if your aircraft is placarded against the maneuver, then don't do it.  Don't know how you'll land a still crosswind, though.

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So I am the op, I thank you for the enthusiastic dialogue. Honestly I am going with guys like mike e and don k and the test pilots.  I asked ab  IIt slips for a reason  and I did get my answer.  I would rather fly comfortably within the envelope.  Some would say I’m wrong for not testing the pl e to its limits but for me Im not going to play with the thin edge of the envelope. I have about 650 hours in a variety of Mooney aircraft. I only have 100 hours in the bravo. It’s an interesting plane to learn but I’m not even close to wanting or needing to be a test pilot.  So some might say I’ll never know the plane well enough if I don’t test the edges. I’ll Work on being the best pilot I can be  and I can Confirm having pushed  the limits and messed up at times on landings and other things but I’m in one piece as is the plane. It does take some time to learn this plane and to get it nailed. So thank you all for the input. Good conversation. It confirms what I will or won’t do with the plane.  

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I am with you Mike.  This particular subject has been discussed on this forum for around ten years.  I don’t know, maybe there are some people who joined recently and don’t understand the issue, it is a little frustrating that sound advice has apparently not gotten out.  All I can say is I have a K, I have done lots of stalls, accelerated stalls, power offs, chandelles, slow flight, etc., but I would not even consider a cross-controlled slip under 85 and I don’t care what kind of slip you call it.  Thanks for taking the time to publish yet again the good advice from Bob Kromer.

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I just don’t get it, information was provided by two prominent Mooney Specific pilots , Master pilots at that, summaries of a competent Mooney test pilot who has taken our planes to the edges and beyond, kept quality notes of the various flight profiles.

Even this isn’t enough information for some pilots to either accept, comprehend or digest, rather they provide unsubstantiated opinions masquerading as fact. Mike I’d just keep form letters ready as needed.

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I have no experience in models other than my own. But I believe stall behavior is also dependent on model, just from an engineering perspective. They stretched the tail (F/J) without adding weight to the front or changing wing position, that has to result in a more balanced plane and less likely to drop the nose during a stall. After J they extended the nose and added more weight forward.
So anytime someone makes a blanket statement about behavior of all Mooneys, I take it with a grain of salt.


Tom

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So, I'd like to 'slip' the conversation to the same topic, but from a different angle. It was pointed out to me in a tactful private message that I confused a forward slip and a side slip. I argued my point, but was shot down by FAA Documentation.  I guess officially, a side slip is used on landing and a forward slip is used to reduce speed/altitude etc.  But I still think this is bass-akward!  I know I won't win my argument, but I lay it out anyway to see if someone can help make sense of it.

My reasoning is that a "forward slip" is used to maintain the correct forward direction of the longitudinal axis, as required for landing in a cross wind. Whereas a side slip is one where the longitudinal axis of the plane is shifted to one side or the other of forward direction, thus presenting the "side" of the airplane to the desired path (and creating the drag which in fact provides the desired benefit).  In fact, the relevant section of the FAA Airplane Flying Handbook agrees that this is exactly what is happening! (See pages 8-11 and 8-12 of the attachment.)  So my explanation seems logical to me, but still, I always have them officially backwards.

Can anyone give me a better way to think about why a side slip is named thusly, and also a forward slip? Otherwise I am doomed to just say "I slipped the airplane" and give up trying to distinguish between the two.  :D

 

10_afh_ch8.pdf

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7 hours ago, steingar said:

Now, if your aircraft is placarded against the maneuver, then don't do it.  Don't know how you'll land a still crosswind, though.

**Caution**:  You are about to read a comment meant to be part sarcasm and part humor, not to be taken too seriously:

Perhaps some transition training in a long body Mooney taught by @mike_elliottwould help you to understand how to handle crosswinds safely and effectively.  

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30 minutes ago, Jeff_S said:

So, I'd like to 'slip' the conversation to the same topic, but from a different angle. It was pointed out to me in a tactful private message that I confused a forward slip and a side slip. I argued my point, but was shot down by FAA Documentation.  I guess officially, a side slip is used on landing and a forward slip is used to reduce speed/altitude etc.  But I still think this is bass-akward!  I know I won't win my argument, but I lay it out anyway to see if someone can help make sense of it.

My reasoning is that a "forward slip" is used to maintain the correct forward direction of the longitudinal axis, as required for landing in a cross wind. Whereas a side slip is one where the longitudinal axis of the plane is shifted to one side or the other of forward direction, thus presenting the "side" of the airplane to the desired path (and creating the drag which in fact provides the desired benefit).  In fact, the relevant section of the FAA Airplane Flying Handbook agrees that this is exactly what is happening! (See pages 8-11 and 8-12 of the attachment.)  So my explanation seems logical to me, but still, I always have them officially backwards.

Can anyone give me a better way to think about why a side slip is named thusly, and also a forward slip? Otherwise I am doomed to just say "I slipped the airplane" and give up trying to distinguish between the two.  :D

 

10_afh_ch8.pdf 23.57 MB · 2 downloads

Nope.  It truly is bass-ackwards :D

The only way I can remember it is to think that in a side slip, I'm facing forwards but moving sideways.  In a forward slip, I'm facing sideways but moving forwards.  Technically, though, they're the same maneuver, they're just named differently in different arbitrary frames of reference.  I'm with you in just saying "slip"...

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The sideslip is the cross-controlled maneuver you use to keep the axis of the aircraft parallel to the center line and to keep the aircraft from moving to the right or left off the centerline during a crosswind landing.  The forward slip is the cross-controlled maneuver you use generally on final to lose altitude more rapidly without gaining airspeed.  From an aerodynamic standpoint, in the side slip you are using bank to move the aircraft relative to the crosswind component, by the same amount that the crosswind is trying to move you off the centerline, so the rudder is away from the wind and the bank is in to the wind.  In a forward slip, you just slip one way or the other on final. The main difference between the two is that during a sideslip, if you have done it right, you are in ground effect and right above the runway. If the maneuver increases the stall speed the aircraft has a very short fall to the runway surface, and the closer you are to stall speed at the moment you land the better.  In the forward slip you may have a few hundred feet to fall but you have one advantage, and that is you are descending faster than during a sideslip and hoping that the unloading of the wing will keep you from stalling.  As far as I am concerned, and I know others may dispute this, both are cross-controlled maneuvers and the potential for a stall is there in both.  If you are heavily trimmed up, the need for the elevator to fly is there in both maneuvers.  The saving grace of the side slip is that you do not have far to go to the runway surface, unless, of course, you have started the maneuver too far above the runway.  Then you will have the same problem with a stall as does the foward slip.

Edited by jlunseth

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