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Porpoise landing

Hi!

What can cause the porpoise landing in the landing gear?
What can get hurt?

How strong the retractable landing gear on TB?

Z.

Greece

My understanding of what is meant by a porpoise landing is when the pilot attempts to force the aircraft onto the ground when it’s still traveling too fast to land.

They force it down (nose first) and the aircraft bounces, so they force it down harder, it bounces again. Repeat this a few time until either the speed slows enough to stay on the ground or the nose wheel breaks.

The cause it incorrect pilot technique not the landing gear.
What can get hurt is the nose gear (and potentially a lot more if it breaks).

EIWT Weston, Ireland

Not sure about the TB20s (I only got 2h on the TB9 which is not even RG) but I fly Mooneys J & K and they like to bounce due to heavy nose & airframe geometry, you should really go-around when bounce amplitude does not decay on the 2nd bounce (3rd bounce and off you go for engine + prop shop)

The Mooney bounces on takeoff/landing happens,
1) on flat tarmac in high nose attitude when flaring to land slow or on early liftoff for takeoff
2) on bumpy grass when coming on fast GS irrespective of the nose attitude as you hit bumps

For Mooney, aside from stable approach and adequate power/speed, one way to cheat is to kill dramatic bounces on takeoff/landing by keeping some sideslip while any of the main wheels is on the ground, even with no cross winds, it just dissipate pitch PIO and you will have more control when aircraft flies or stick on ground without adjusting pitch/power…

The 1st advice is to fly a stable approach into good runways, the 2nd advice is to go around, the 3rd advice is to land with slowest ground speed with controls slightly crossed, any pitch/contact oscillations are converted into lateral wiggles (main wheel tires seems less expensive than prop+engine )

There is literally not much you can do about bouncing with pitch/power once is starts (other than neutral pitch & zero power and hope for the best or neutral pitch & full power and give it another go ), the physics are really complicated as in ground effect near or bellow stall speed pitch/power will have a non intuitive behaviour anytime your front wheel touches the ground or anytime the ASI speed crosses your stall speed as adjusted by vertical acceleration or wheel-surface normal/friction forces, in other words you will have no clue if you are flying, driving, free fall or in accelerated stall and you will be confusion each regime for the other, while aircraft is flying you

Last Edited by Ibra at 22 Jul 22:07
Paris/Essex, France/UK, United Kingdom

Ibra wrote:

There is literally not much you can do about bouncing with pitch/power once is starts (other than neutral pitch & zero power and hope for the best or neutral pitch & full power and give it another go )

My experience is different, including in Mooneys. Neutral pitch control input is an entry point to bouncing, not an exit strategy. Any flying error which allows the plane to change pitch close to the surface invites a bounce, and another, and so forth, until either the pilot corrects, or the plane fails. If I bounce an airplane at all while landing, I will be dis-satisfied with my technique. I certainly will not accept a bounce as “I couldn’t have done anything about it.”.

Sure, every now and then, a landing is not as smooth as you wish, particularly on uneven ground. If you have allowed the plane to bounce enough that at the top of the bounce, you are not confident that you could re-flare, and land power off, go around. If it’s a small bounce, maintain the pitch attitude (certainly do not allow it to pitch down at all!), and then as you near the runway again, flare and land.

If you hear the stall warning horn peep just as you touch, it is extremely unlikely that you will bounce – the plane is stalled, and really does not want to fly anymore. If you are uneasy about flying to the stall warning horn in the flare, that’s okay. Once you touch down, hold the nose off, and raise it a little. Hear it now? If so, it was probably a decent landing. A non bounced landing will be the entry to a stall, you will just nicely grease it on before the nose drops in the stall. ‘Could be 5 knots before the nose drops, or 1 knot, as long as you land on the mains first (tricycle). 10 knots too fast, and it’s going to climb when you flare, and there could be a bounce in there too, if you touch at that speed.

Leaf spring gear tends to be more bouncy (no oleo damping effect). Older tricycle Cessnas, and all original taildragger Cessnas have leaf spring gear, and they will rebound you into a bounce if you land too hard and too fast (both elements of that will be required for a bounce). The Mooney rubber block suspension can be a little bouncy, but not so bad as to provide an excuse for bouncing landings.

I agree that if there is a crosswind, touching one mainwheel before the other will aid a little in arresting a bounce tendency. However, I would not crab an airplane onto a runway needlessly. Tire wear, landing gear side load, and the slightly increased risk of heading off the runway, are not worth the very slight advantage in not bouncing, just work on your technique to not bounce. Certified airplane landing gear is all adequately bounce resistant. It will have met the following requirement:

Sec. 23.75

Landing.
……………….
(b) Airplanes of 6,000 pounds or less maximum weight must be able to be landed safely and come to a stop without exceptional piloting skill and without excessive vertical acceleration or tendency to bounce, nose over, ground loop, porpoise, or water loop. Quote

If, when I test flew an airplane for certification, I could not land it without bouncing it, I would not sign off on it. If I bounced it the first time, I would blame my technique first, and practice a little.

If you’re having trouble with bouncing landings, seek some training, it’s not the plane….

Home runway, in central Ontario, Canada, Canada

How strong the retractable landing gear on TB?

It is quite strong but obviously there are limits. I know of nose gear damage, not quite broken off, in a landing with a ~50kt headwind down the runway (no idea why that was a problem; perhaps the wind shear was not allowed for). I don’t know of main gear damage, where somebody touched down on a runway (I know somebody who broke the gear off hitting a piece of concrete before the runway start).

What is also possible is a prop strike, in a “wheelbarrow” type landing (pushing the nose down, instead of holding the nose gear off) without damaging the nose gear.

And never let a fire crew pull the plane out of being stuck in mud, by attaching a rope to the nose gear. Attach the rope to the two main gear legs.

Administrator
Shoreham EGKA, United Kingdom

I have only once seen the outcome of a damaging ‘porpoise landing’, a PA38 at a local, fairly smooth grass strip. The prop blade slices to the turf were clearly visible as they then arced off to one side into the longer grass where the aircraft nosed over on to its back. That was a write off though the pilot walked away, so I suppose the common wisdom would call that a ‘good landing’!

If you hear the stall warning horn peep just as you touch, it is extremely unlikely that you will bounce – the plane is stalled, and really does not want to fly anymore.

I don’t think I have ever, in my admittedly limited experience, come across a stall warner that peeped actually at the stall. They all seem to sound quite a bit before that.

Last Edited by ChuckGlider at 23 Jul 08:31

I did very bouncy landing on my very first solo, with the Aquila A210. In hindsight, I came in too fast, trying to land at perhaps 70 kts and with unrefined flare technique. A series of bounces followed, one worse than the next, with the last one propably catapulting me several meters into the air. I applied full power and went around successfully. Trying to land from that last bounce would certainly have resulted in a crash, given my lack of experience and skills at that point.

I have the event on video, captured by my wife, who unfortunately witnessed it and was quite put off from flying with me by that. The next landing was fortunately a good one, although the realisation that nobody else but me could get the plane down safely was unnerving back then.

That was the last time I had a really bouncy landing, though there have been a few smaller bounces since then, usually after not flying for months.

Low-hours pilot
EDVM Hildesheim, Germany

Peter wrote:

What is also possible is a prop strike, in a “wheelbarrow” type landing (pushing the nose down, instead of holding the nose gear off) without damaging the nose gear.

Yes that is improper landing technique, coming fast and pushing stick forward to land on higher speeds than the stall (basically landing with the stick rather than stalling ), but you can also get bounces and prop strike while holding stick well back bellow the stall speed then hitting a bump or gust (basically abusing soft field techniques on hard surfaces, grass/tarmac does not matter, I know it is obvious but people do it )

Last Edited by Ibra at 23 Jul 09:29
Paris/Essex, France/UK, United Kingdom

Pilot_DAR wrote:

My experience is different, including in Mooneys.Neutral pitch control input is an entry point to bouncing, not an exit strategy….If you have allowed the plane to bounce enough that at the top of the bounce, you are not confident that you could re-flare, and land power off, go around. If it’s a small bounce, maintain the pitch attitude (certainly do not allow it to pitch down at all!), and then as you near the runway again, flare and land.

You always have a different flying experience

Yes, I agree go-around if the main wheels leave the ground and you don’t have energy to flare again otherwise you can save some, but what about keeping away from bouncing on uneven ground when mains are in “drive mode” and you are bellow stall speed?

Last Edited by Ibra at 23 Jul 09:50
Paris/Essex, France/UK, United Kingdom

There was a famous youTube of a Brasilian Cessna 180 being planted, with a capital P, in a wheel landing with too much speed, and after a bunch of PIO bounces it finally threw in the towel and nosed over.

I can’t find it now, but a few years back it was a classic.

Land at the correct speed, easy to say, but is the main prevention tool.

Oxford (EGTK), United Kingdom
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