Porpoise after landing

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DaveInPA

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Today I came in to land in a relatively normal approach. My flare was uneventful from what I remember but after I touched down my plane started to go up and down a bit and after 3 of those it got so significant that I gunned it and just went around.

im well aware of a classic bounced landing that can turn into a porpoise situation if not controlled. This wasn’t that - I didn’t land hard or bounce and it was more like my nose gear just did the bouncing. I hesitate to use the word “bounce” since I think my mains were on the ground the whole time.

curious if anyone has had a similar experience and or could shed some light on the root cause of something like this.
 
It was a gusty day so maybe 5kts more than normal. That would keep me floating but after touch down maybe I still had some energy?
 
Good on you. Increasing amplitude oscillation is certainly textbook porpoising. Oakum’s razor applies.

You powered your way out instead of trying to salvage the landing. Take the win.
 
Dave - you will find that additional backpressure on the stick will fix a lot of the landing problems you might have. If I had to guess, you were very flat in the landing attitude with minimal backpressure, and you were working the nose strut which those two together started the oscillations. What part of PA are you in? Would be happy to work with you if you're anywhere within an hours flight of Harrisburg.
 
Had to be too fast. If you were on speed, and truly *landed*, the plane would not have the energy to porpoise.
 
DaveInPA said:
Today I came in to land in a relatively normal approach. My flare was uneventful from what I remember but after I touched down my plane started to go up and down a bit and after 3 of those it got so significant that I gunned it and just went around.

im well aware of a classic bounced landing that can turn into a porpoise situation if not controlled. This wasn’t that - I didn’t land hard or bounce and it was more like my nose gear just did the bouncing. I hesitate to use the word “bounce” since I think my mains were on the ground the whole time.

curious if anyone has had a similar experience and or could shed some light on the root cause of something like this.
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What airplane?
 
Arbiter419 said:
Dave - you will find that additional backpressure on the stick will fix a lot of the landing problems you might have. If I had to guess, you were very flat in the landing attitude with minimal backpressure, and you were working the nose strut which those two together started the oscillations. What part of PA are you in? Would be happy to work with you if you're anywhere within an hours flight of Harrisburg.
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Yea I think you are right. When I started training in my plane I noticed similar, but much much less, motion on take off. Then I realized I was putting forward pressure on The yolk to keep it on the ground until Rotation speed. I must not had enough back pressure all the way through round out.
 
Anybody else fly the plane recently Or played with the seat height?? I have no twin experience but In our club plane what screws me up the most is when anothe member changes the seat height. Just screws my sight picture at the end snd I just don’t pull back enough to stall it on the runway. Flying a 182.
 
If the mains never left the ground it wasn’t a porpoise. A porpoise would include a noise down attitude (the bad part of a porpoise), which can’t happen if the mains are on the ground.
 
Salty said:
If the mains never left the ground it wasn’t a porpoise. A porpoise would include a noise down attitude (the bad part of a porpoise), which can’t happen if the mains are on the ground.
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Not certain that’s true.
ETA: perhaps I misread your post. If the mains NEVER leave the ground you are correct. I took it as the initially did not leave the ground.
 
Kritchlow said:
Not certain that’s true.
ETA: perhaps I misread your post. If the mains NEVER leave the ground you are correct. I took it as the initially did not leave the ground.
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Well, I did miss the “I think” in my first read.
DaveInPA said:
I think my mains were on the ground the whole time
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DaveInPA said:
I didn’t land hard or bounce and it was more like my nose gear just did the bouncing. I hesitate to use the word “bounce” since I think my mains were on the ground the whole time.

curious if anyone has had a similar experience and or could shed some light on the root cause of something like this.
Click to expand...
I've had a few rentals that did that to me and a few others that had a shimmy on rollout. Full aft on the yoke until stopped generally cured both.
 
You could call it an incipient porpoise. The cause is the same, higher speed.

or, it could be that you flopped it down, dropped the nose down hard and it started bouncing.
 
bflynn said:
or, it could be that you flopped it down, dropped the nose down hard and it started bouncing.
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Or you let the nose down before the airplane wanted it to be down. Hold the nose up as long as you can. Don't stop flying the plane until it's parked.
 
If a plane is capable of porpoising it is capable of flying. Landing speeds shouldn’t support porpoising.

The only way an airplane will porpoise is when the elevator is calling for more AOA. Push the yoke forward a little and it’ll fix that.
 
Rule of thumb: if the nose wheel ever hits first, go around immediately. Don't think about it. Don't try to salvage it. Full power and go around.

If you bounce on the mains with nose up attitude, a bit of power will cushion your second landing, but again if the nose wheel hits first, immediately go around.
 
Porpoising is almost always a result of touching down with too much speed. Remember that AoA and airspeed are inseparable, and a high speed in the flare means a low AoA which means a nose-low attitude just above the runway, and the nosewheel will hit first and boink the nose up. Flaps make the attitude even worse. Pushing the wheel forward can easily result in expensive noises. Don't do it. It's called PIO. Pilot-induced oscillations.

So review the basics of airspeed and AoA. And then slow down, start the round-out earlier and higher, and get rid of all that speed before touching down. Landings will improve immensely.
 
Too fast. Not in a proper nose high attitude. Because...see previous sentence. You did good by going around, although I wouldn't wait for the third oscillation next time. If you do this in a Grumman there is a good chance of winding up in a heap. You can't porpoise if you land mains first in a nose wheel plane. That means getting to a proper landing speed with a nose high attitude. Cherokee trainees are famous for making three point landings with trike gear. It's a bad habit. If you do it right you can land on the mains and continue holding the nose off until air braking kills enough speed the elevators no longer have enough authority to hold the nose up. If you have enough runway this saves your brakes, too.
 
chemgeek said:
...You can't porpoise if you land mains first in a nose wheel plane. ...
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It can happen. I've seen a landing where the mains hit first, the plane rebounded into the air, pilot must have shoved forward on the yoke to get back down, nose wheel then hit first, mains slammed down, rebounded, repeated, then CFI executed a go-around.
 
Domenick said:
It can happen. I've seen a landing where the mains hit first, the plane rebounded into the air, pilot must have shoved forward on the yoke to get back down, nose wheel then hit first, mains slammed down, rebounded, repeated, then CFI executed a go-around.
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Except the mains didn’t hit first on the second bounce in your example, proving his point.
 
The idea that airplanes rebound or bounce into the air is incorrect. The only way the wings can support the weight of the airplane is because they’re at flight speed.
 
Domenick said:
It can happen. I've seen a landing where the mains hit first, the plane rebounded into the air, pilot must have shoved forward on the yoke to get back down, nose wheel then hit first, mains slammed down, rebounded, repeated, then CFI executed a go-around.
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Had it happen to me yesterday. Piper Archer, light loading, rough as a cob, gusty 90 degree crosswind, 75kts on high steep final, left wing down crab. At about 50 feet, the bottom fell out so I goosed the throttle. At touchdown, left main first then right, nose high. three chirps on the mains and then nosewheel touchdown. It can bounce on the mains. Nobody died :)
 
Domenick said:
It can happen. I've seen a landing where the mains hit first, the plane rebounded into the air, pilot must have shoved forward on the yoke to get back down, nose wheel then hit first, mains slammed down, rebounded, repeated, then CFI executed a go-around.
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That's PIO. The classic video (though the nose hit first):


Note the high speed, meaning a low AoA and nose-low attitude. Way too much flying speed. I think an awful lot of pilots missed that groundschool class. When high on final, go around. Don't dive at the runway. You can't fix it. You just end up with too much speed.
 
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Bouncing on the mains with a continued nose up attitude is not an issue. The problem comes in one of two ways -

1) the speed is high, which means a more nose down pitch and a higher chance of the nosewheel striking first.
2) the speed is lower, so when the mains bounce, there isn't enough elevator authority to hold the nose up. The bounce happens from dropping the airplane onto the runway, but if your speed is high enough, you can keep the nose up. If not, the nose drops as elevator authority is lost, resulting in the nose wheel striking first.

In either case, with decaying speed, the nose will drop resulting in the nose wheel striking first. The nose wheel hitting first produces a "galloping" bounce which gets more rapid with each iteration.
 
Dan Thomas said:
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Note the high speed, meaning a low AoA and nose-low attitude. Way too much flying speed. I think an awful lot of pilots missed that groundschool class. When high on final, go around. Don't dive at the runway. You can't fix it. You just end up with too much speed.
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Also, what to do when your somewhat high is counter intuitive. Don't point the nose at the numbers, get all of your drag out, pull to idle, and hold your altitude until your speed gets down to landing speed. Even the slick Mooney drops somewhat like a rock with flaps and gear out, engine at idle, and airspeed of 63-65kts. Of course you need enough of an airspeed cushion to have energy for the roundout and flare.
 
Bill said:
Also, what to do when your somewhat high is counter intuitive. Don't point the nose at the numbers, get all of your drag out, pull to idle, and hold your altitude until your speed gets down to landing speed.
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And for best effect, do the above out of ground effect.
 
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