Can a really aggressive forward slip on final ever produce a spin?

[mike_elliott]

4 minutes ago, Tony Armour said:

Mike, was that due to a slip ? 

What do you feel about them with plenty of airspeed ? I just have never felt the first issue. I'll admit, I've never (that I recall) heard that slips could be an issue.

Max Rae probably had 10K to 12K mooney hours under his belt, and Joel Smith was reported above 15K, and a former factory "driver". That is a whole lot of Mooney time in the front 2 seats.

 Max loved to aggressively slip on final, perhaps one time too many. From what I hear, the plane rolled over on its back and stalled on short final.

Keeping the speed up is key if your are not coordinated. Flaps on your long body disturb the airflow over the tail and can promote air separation, more so than in the mid and stubby body Mooney's. In the Bravo, you have all kinds of tools to get stabilized on approach as you know, Tony. I like to error on the safe side and would just go around if all is not "on speed, on slope" at 1 mile final. I'm too old to want to fly with my butt above my head anymore

[salty]

Seems like most of this conversation is revolving around final with flaps. What about decents without flaps in a short body? That's when I've found myself wanting to slip to lose altitude without gaining too much speed -  before gear is down > 120. I haven't started IFR yet, so once I'm at pattern altitude, if I'm needing a slip on final, I'm doing something very wrong and a go round is probably warranted. 

[Yetti]

Then why would you not throw out the bottom speed brakes to slow down.  Pull up a bit get the airspeed down to gear speed, then throw down the speed brakes.  You are going to need them eventually.

[salty]

35 minutes ago, Yetti said:

Then why would you not throw out the bottom speed brakes to slow down.  Pull up a bit get the airspeed down to gear speed, then throw down the speed brakes.  You are going to need them eventually.

I suppose so. It just seems odd to put down gear at 4000 feet. 

[Yetti]

Oh up high.  I thought we were talking approach.  pull the throttle, put it in a 45 degree bank.

[Andy95W]

I've been trying to figure out why this is even a thing for the long bodies.  Your gear and flap speeds are so high compared to the legacy models, why not just throw everything out and take benefit of all that drag?  Why would you even need to do a forward slip?

(M20C gear and flap speeds 120/100 MPH.  Yes, miles per hour.)

[carusoam]

Keep an eye on the critical nature of the title...

1) hitting the brakes at 4k' AGL leaves a tremendous amount of room to recover from a mistake. While the adjustment in speed or altitude is typically spread over a longer period of time. Kind of like hitting the brakes on the highway, When letting off the gas pedal will usually do...

2) using full slips and speed brakes are strong braking maneuvers.  Not typically used on an ordinary flight until close in. It is un-Mooney in terms of speed and efficiency.

3) maximum E-descent in a Long Body is done at gear down speed, with the gear and speed brakes out, max rpm, throttle out...check on gear operating speed v. Gear extended speed, slow to extension speed, increase to gear down operating speed.  The vertical speed generated doing this is tremendous.  You will be on the ground in a few minutes.  Any more braking required is an extreme emergency like a fuel fire in the cabin and there are no set rules for that...

4) flaps are not part of the equation because flap speeds are too low and too efficient for max braking... flaps used outside their normal range risks bending and braking parts.  After an E-descent, it may be good to have usable flaps for the landing....

5) aerodynamic breaking increases with the square of airspeed.  Going fast (140kias) with the brakes out dissipates a lot more energy than when you are ten knots fast (90kias) trying to lose a few hundred feet.

6) Speed brake redline is typically Vne. LB Gear operating speed is 140kias 

This is like energy management 102.  Slightly more advanced than 101.

PP thoughts only, not a CFI... let me know if I missed something...

Best regards,

-a-

 

[carusoam]

Andy, I updated my previous post to try and include your above thought...

the dp is hard to fix... 

Best regards,

-a-

[bonal]

This has been a real good thread and like so many here has added to my thinking as is applies to my flying. As someone who uses a forward slip as a normal option for reasons I have mentioned and the need to fly close patterns because of tighter airports from time to time I have really been more aware about the way I fly my airplane and really thinking about wing loading angle of attack airspeed airplane loading and winds and how they have an important effect on all those things. Really want to thank all that add their  experience for everyone's benefit 

edit

and these are things I learned in basic flight training but all the different discussions over the few years here and my continued flight experience really puts them into light.  A license to learn.

[Danb]

Mike I was ready to outline my slipping thoughts in the Bravo unlit I reread your two posts of which I greatly concur.

[jlunseth]

11 hours ago, Tony Armour said:

Mike, was that due to a slip ? 

What do you feel about them with plenty of airspeed ? I just have never felt the first issue. I'll admit, I've never (that I recall) heard that slips could be an issue.

I looked through the NTSB report about a week ago and it looked more like a too tight base to final, the plane then rolling inverted and nose down.  Maybe he was trying to slip in the turn, which would not be good.  But the main point to take from that accident is that no matter how many hours you have nor how much skill, the rules of aerodynamics apply equally and mercilessly.  Greater skill does not let you opt out of them.

[Tony Armour]

13 hours ago, salty said:

Seems like most of this conversation is revolving around final with flaps. What about decents without flaps in a short body? That's when I've found myself wanting to slip to lose altitude without gaining too much speed -  before gear is down > 120. I haven't started IFR yet, so once I'm at pattern altitude, if I'm needing a slip on final, I'm doing something very wrong and a go round is probably warranted. 

You got me thinking. Would I usually be at full or one notch of flaps. Dang it, getting old sucks. 

 

12 hours ago, N1395W said:

I've been trying to figure out why this is even a thing for the long bodies.  Your gear and flap speeds are so high compared to the legacy models, why not just throw everything out and take benefit of all that drag?  Why would you even need to do a forward slip?

(M20C gear and flap speeds 120/100 MPH.  Yes, miles per hour.)

Not that it should still be done but like recently I got to descend from 11,500' in 30 miles. Sometimes there just aren't enough miles to get the job done. I honestly don't remember but I think I opted to fly downwind and land back to the SE (instead of slipping etc) I would have done that to burn off speed and any altitude left. I guess slowing down and coming down would have worked too but part of the secret agreement to flying high and doing all that climbing is that you get to haul ass coming back down.  Doesn't look really fast on paper but there was a little headwind that day. 

https://flightaware.com/live/flight/N40ZM

[PTK]

10 hours ago, jlunseth said:

I looked through the NTSB report about a week ago and it looked more like a too tight base to final, the plane then rolling inverted and nose down.  Maybe he was trying to slip in the turn, which would not be good.  But the main point to take from that accident is that no matter how many hours you have nor how much skill, the rules of aerodynamics apply equally and mercilessly.  Greater skill does not let you opt out of them.

This has me thinking. We know in the base to final the airplane is low, slow, banking, maybe a tad uncoordinated and the stall speeds are higher. The one thing that's next to impossible to know is how slow was the airplane allowed to get in the turn and what the pilot did to encourage and precipitate a stall spin. This may have not been the cause in this particular accident due to the two very experienced pilots but it may very well play a role in other base to final stall spins. I'm specifically referring to flaps. Introducing drag in a turn with flaps only aggravates things and this is the worst turn to throw in flaps. The airplane is already on the edge and the last thing it needs is to pitch up and slow even more. Depending on how close to the edge it is, flaps in the turn may very well be enough to through it over the edge. And that's the last thing that poor pilot will ever do in his/her life.

Often times this concept of the order of doing things may not be clear especially to newer pilots leading them to develop sloppy flying. And this kind of sloppiness is dangerous. I know my ppl instructor was not that detailed. It wasn't until my IFR training that a different instructor drove it into my head  to "never add flaps in a turn" along with flying by the numbers. 

My apologies for the drift here. We now return to our regularly scheduled program!

[Hank]

Hmmm . . . Lowering flaps in my Mooney pitches the nose down, not up, which would put me further from a stall, not closer to it . . .

[PTK]

Although TO flaps increase lift by shifting it to the rear of the wing causing a pitch down, with anything beyond TO flaps the drag will exceed any lift and will initially momentarily pitch up. 

[salty]

Huh? Every notch of flaps causes my mooney to pitch down. 

[PTK]

The point is that as flaps are introduced the angle of attack increases momentarily and the airplane initially wants to climb before it pitches for its trimmed airspeed. In a turn especially base to final with uneven lift where one wing is producing more lift than the other is no time to be add drag into the equation.

[salty]

22 minutes ago, PTK said:

The point is that as flaps are introduced the angle of attack increases momentarily and the airplane initially wants to climb before it pitches for its trimmed airspeed. In a turn especially base to final with uneven lift where one wing is producing more lift than the other is no time to be add drag into the equation.

That makes sense to me. 

[bonal]

3 hours ago, Hank said:

Hmmm . . . Lowering flaps in my Mooney pitches the nose down, not up, which would put me further from a stall, not closer to it . . .

This is true but as the nose drops if the pilot tries to hold the nose up he / she is increasing AOA and wing loading and if near stall could be enough for a tragic result. I was also drilled by my instructor never add flaps while in a turn.

[jlunseth]

Well, deploying flaps lowers stall speed at every bank angle.  It is a good precaution to have at least half flaps in on the base to final turn.  I sometimes do that - deploy flaps for the base to final - even if the wind conditions are such that I am going to land half flaps or no flaps.  In fact, I do that especially in that scenario.  Strong gusty crosswinds will often cause you to blow through final on the turn, and that causes the temptation to use rudder to point the nose at the runway, making you uncoordinated when you least need to be.  Having flaps deployed is protection against a stall.  I will then raise them on short final for landings in gusty crosswinds where I need speed and therefore rudder authority.  It also helps of course to be descending, which decreases the load on the wings. It helps to be descending regardless of nose angle because that lowers the load on the wings.  The last thing you want to do in an overturned base to final is to rudder the nose to the runway and level off at the same time.  Might be a good time to add some power and improve the airflow over the wings if you really need to be doing something like that.

[Tony Armour]

I flew this afternoon. Slip on final (because of this thread) Gear out, full flaps, 85 knots, nose pointed down, full left rudder. Really no different than any other time in the last 11 years with the Bravo. I think the 201 was pretty much the same seven years before that....maybe a tad slower. I've never felt the airplane unstable or do anything weird. 

[Guitarmaster]

Yep.  I slip my 'F' all the time... well, when high and fast.  

Nose pointed down at around 100 mph.  Make sure fuel is selected to the trailing wing so it doesn't unport. Rudder as necessary (usually on the floor).  Falls out to the sky like a brick.  No weird aerodynamic tendencies or vibrations.  I remove the slip before increasing AOA.