Porpoising on take-off?!
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Porpoising on take-off?!
Hello all!
Ive just joined a new flying club and I am currently filling out paper work to assess my skills. One of the questions is 'How would you handle porpoising on take off'? I've heard of porpoising on landing, but not on take off.
I can only imagine that it would happen if you tried to pull back at too low an air speed? You could take off momentarily due to ground effect, but that's all. The action that I would take is to make sure that full power was applied, let speed build up and then pull back. HELP?!
Has this ever happened to any one?
Thanks!
Ive just joined a new flying club and I am currently filling out paper work to assess my skills. One of the questions is 'How would you handle porpoising on take off'? I've heard of porpoising on landing, but not on take off.
I can only imagine that it would happen if you tried to pull back at too low an air speed? You could take off momentarily due to ground effect, but that's all. The action that I would take is to make sure that full power was applied, let speed build up and then pull back. HELP?!
Has this ever happened to any one?
Thanks!
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porpoise
I've never heard the expression,but "googled" it, and basically it is trying to lift off before correct flying speed is reached ,promoting a series of mini stalls,dives and climbs along the runway.
Answer must be to lower nose a little and wait until correct speed is reached.
I'm sure you will have much more experienced pilot replies than mine.
Lister
Indoors because there is a 25 knot crosswind!
Now going gardening.
Answer must be to lower nose a little and wait until correct speed is reached.
I'm sure you will have much more experienced pilot replies than mine.
Lister
Indoors because there is a 25 knot crosswind!
Now going gardening.
The term "Porpoising on take off" sounds to me as somebody is trying to describe a pitch circuit pilot induced oscillation (Pitch PIO). The best way to deal that is usually to stop chasing the pitch attitude on the stick/yoke.
So, the short answer is keep the pitch control still in about the right place, then make only small slow adjustments.
I use to have a little Canard single seater called a Goldwing which did this very readily; it's likely a consequence of either an aeroplane with a lightly damped longitudinal short period mode, or a pilot who is too ready to make rapid control inputs (or both together!)
I've never heard of a flying club that set a written exam for entry before? Whereabouts is this - an unusual way of doing things.
G
So, the short answer is keep the pitch control still in about the right place, then make only small slow adjustments.
I use to have a little Canard single seater called a Goldwing which did this very readily; it's likely a consequence of either an aeroplane with a lightly damped longitudinal short period mode, or a pilot who is too ready to make rapid control inputs (or both together!)
I've never heard of a flying club that set a written exam for entry before? Whereabouts is this - an unusual way of doing things.
G
1. Don't attempt to unstick (I hesitate to use the word 'rotate' for some light aircraft!) before the correct speed.
2. Select, hold and trim the correct attitude.
That said, I did once get into a nasty pitching oscillation in a PA28 after landing whilst attempting the same 'hover taxy' technique which worked OK in a Bulldog to expedite runway vacation. My own stupid fault, no damage but I Learned From That!!
2. Select, hold and trim the correct attitude.
That said, I did once get into a nasty pitching oscillation in a PA28 after landing whilst attempting the same 'hover taxy' technique which worked OK in a Bulldog to expedite runway vacation. My own stupid fault, no damage but I Learned From That!!
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Thanks Lister, Genghis, Beagle for taking time to reply to my msg ... I really appreciate the advice that you've offered.
Genghis ... the question was from a sheet of questions that I have to answer before I can be 'signed off' by an instructor, just to check that i'm (or anyone else) not going to do anything silly/dangerous. There are other qu's that I would have expected to get asked as well, such as, how would I deal with an engine failure/ how would I deal with an engine fire on start-up, etc.
regards, PC
Genghis ... the question was from a sheet of questions that I have to answer before I can be 'signed off' by an instructor, just to check that i'm (or anyone else) not going to do anything silly/dangerous. There are other qu's that I would have expected to get asked as well, such as, how would I deal with an engine failure/ how would I deal with an engine fire on start-up, etc.
regards, PC
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That's interesting, as the aircraft that i'm choosing to fly is a PA-28. I think they're lovely to fly. I've never had a porpoise on take off at all ... in all my grand total of 67 hours
! Mind you, i've never taken off/ landed on a grass strip, I think the nearest one to me is Barton. I bet its really bumpy to land on a grass strip 
?
! Mind you, i've never taken off/ landed on a grass strip, I think the nearest one to me is Barton. I bet its really bumpy to land on a grass strip ?
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Can you really asses a pilot's skills by giving them written scenarios and ask them to fill them in at home?
What's wrong with instructional training, technical questions and then a check-ride?
What's wrong with instructional training, technical questions and then a check-ride?
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Porpoising can occur on takeoff or landing, and may be initially induced by the pilot or by the aircraft. The development of oscillations and their continued occurence, however, is nearly always a pilot issue. I've watched pilots damage airplanes on takeoff and on landing when porpoising.
One of the most common problems is not holding the nose off. Another problem, and I've seen airplanes damaged this way, is trying to force the airplane onto the runway. The airplane wants to fly, the pilot doesn't want it to fly, and the airplane becomes airborne repeatedly with the pilot forcing it back down...it bounces and the fight with the airplane only increases in magnitude until the pilot either gets wise and quits fighting the airplane, or something bad happens. Often it all starts with a bounce.
It's sometimes seen in a conventional gear airplane once the tailwheel is in the air. The pilot keeps pushing forward on the stick trying to hold the airplane on the runway...sooner or later it skips or bounces and the fight's on.
As others noted, it's a pilot-induced oscillation (PIO).
What to do if a porpoise develops on takeoff? Let the airplane fly, or reject the takeoff. Usually the simplest thing to do is to freeze the controls and let the airplane stabilize and then handle it from there.
"Doctor, it hurts when I do this."
"Then don't do that any more."
Still good advice today.
One of the most common problems is not holding the nose off. Another problem, and I've seen airplanes damaged this way, is trying to force the airplane onto the runway. The airplane wants to fly, the pilot doesn't want it to fly, and the airplane becomes airborne repeatedly with the pilot forcing it back down...it bounces and the fight with the airplane only increases in magnitude until the pilot either gets wise and quits fighting the airplane, or something bad happens. Often it all starts with a bounce.
It's sometimes seen in a conventional gear airplane once the tailwheel is in the air. The pilot keeps pushing forward on the stick trying to hold the airplane on the runway...sooner or later it skips or bounces and the fight's on.
As others noted, it's a pilot-induced oscillation (PIO).
What to do if a porpoise develops on takeoff? Let the airplane fly, or reject the takeoff. Usually the simplest thing to do is to freeze the controls and let the airplane stabilize and then handle it from there.
"Doctor, it hurts when I do this."
"Then don't do that any more."
Still good advice today.
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Cabair developed the habit of asking this question and others in the 90s when they had a big fleet of Grumman Cheetahs. I say 'a big fleet', but not as big as it would have been head Grumman fitted as slightly more substantial nose landing gear assembly!
I suspect that the habit has been passed on...
Little point in asking it in what amounts to an 'open book exam' as people will only go around looking the answers up on google or posting the questions on PPRuNE...
Ah. Errrm...
I suspect that the habit has been passed on...
Little point in asking it in what amounts to an 'open book exam' as people will only go around looking the answers up on google or posting the questions on PPRuNE...
Ah. Errrm...
Moderator
Many of the comments, including Guppy's are right on. Proposing can also be casued or aggravated by operating on an uneven, or moving (water) surface, where the support or drag which the aircraft is experiencing from the surface is changing. This can occur on some types during the phase of takeoff when the nose wheel is off, and the mains are just coming off. The mains hit a bump, or catch a small snow drift, and pull the nose down. Then the fight can be on. "Checking" such movement is important, but not always as easy as it sounds.
I don't think that there really is one simple answer to the question as asked, other than to regonize that the conditions have occurred to make this possible, or it is already happening, and to continue to fly the plane. Sometimes PIO is not as easy to overcome as you'd think, particularly on a type which is new to you, while you're still figuring out control feel and optimum attitudes. This makes type training a good idea, even for pilots with lots of experience on other types.
I don't think that there really is one simple answer to the question as asked, other than to regonize that the conditions have occurred to make this possible, or it is already happening, and to continue to fly the plane. Sometimes PIO is not as easy to overcome as you'd think, particularly on a type which is new to you, while you're still figuring out control feel and optimum attitudes. This makes type training a good idea, even for pilots with lots of experience on other types.
.......why?
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I was having a dyslexic moment and thought the thread said "proposing on take off".
"Tortoising" would have been pretty cool as well ! Describes a VERY slow take off run
A helpless hopeless romantic !
"Tortoising" would have been pretty cool as well ! Describes a VERY slow take off run
A helpless hopeless romantic !
Pompey till I die
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Just waiting for the licence
. That 3 week wait is agonising. Only decision now is to either be "captain sensible" and build confidence or whether you take everyone you know flying straight away. I opted for the latter.
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Mike,
More practically: there is a world of difference between rotating a transport aircraft at VR and flying a light aircraft off the ground sympathetically at the right speed.
More practically: there is a world of difference between rotating a transport aircraft at VR and flying a light aircraft off the ground sympathetically at the right speed.
Grumman Tigers and Cheetahs are lovely a/c, but they do get written off because of porpoising
Having had a number of porpoising incidents, one in a C-172 resolved by a go-around and a number in gliders, the key is to recognise quickly what you've got yourself into and then hold attitude.
Porpoising starts with a pitch excursion that is overcorrected and the [over]corrections to the [over]corrections tend to go divirgent; so you do not want to go past the first cycle.
Pick a reasonable pitch attitude for the circumstances and hold the stick there for a few seconds.
Prevention is of course preferable to cure; i.e. don't fiddle with spoilers in the last 50' if not current or in a new glider and think carefully about CG and trim before taking off in that new single-seater.
Grummans when light have a tendency to float past all available runway; so, it helps to reduce the landing speed if you have had a long flight.
Having had a number of porpoising incidents, one in a C-172 resolved by a go-around and a number in gliders, the key is to recognise quickly what you've got yourself into and then hold attitude.
Porpoising starts with a pitch excursion that is overcorrected and the [over]corrections to the [over]corrections tend to go divirgent; so you do not want to go past the first cycle.
Pick a reasonable pitch attitude for the circumstances and hold the stick there for a few seconds.
Prevention is of course preferable to cure; i.e. don't fiddle with spoilers in the last 50' if not current or in a new glider and think carefully about CG and trim before taking off in that new single-seater.
Grummans when light have a tendency to float past all available runway; so, it helps to reduce the landing speed if you have had a long flight.
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The purpose of a rotation speed is to ensure that following the failure of the critical power unit, the aircraft will achieve the screen height by the first obstacle in the take off domain. Therefore it is not applicable to SE aircraft.
Yes yes yes, but effectively to unstick, you pull back on the control column and raise the nose, which is rotation about some axes or other. Glibness aside, I take your point.
More practically: there is a world of difference between rotating a transport aircraft at VR and flying a light aircraft off the ground sympathetically at the right speed.
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"Rotate" is a perfectly acceptable word, found in many light airplane handbooks and training handbooks. It's not out of line, and doesn't describe anything to do with screen heights, minimum control speeds, or multi engine airplanes. It's the act of rotating the airplane from it's ground attitude to it's takeoff attitude or pulling the airplane off the ground if you will. Or simply putting it in a position to "sympathetically" lift off, as one poster noted.
In some advanced performance airplanes, various terms such as V1, Vr, V2, Vmc, etc, apply. And yes, in those contexts, Vr, or V speed Rotate, is a number which is selected to be above the minimum ground control speed in a multi-engine airplane...but it has nothing to do with screen height, either. That would be V2, and really isn't a part of the discussion in this thread.
Feel free to use the word "rotate." It's in common use in the hangar, probably from your instructor, and it's found more than likely in your pilot operating handbook or aircraft flight manual, and most likely in your text book(s) that are used for your basic flying learning and understanding.
In some advanced performance airplanes, various terms such as V1, Vr, V2, Vmc, etc, apply. And yes, in those contexts, Vr, or V speed Rotate, is a number which is selected to be above the minimum ground control speed in a multi-engine airplane...but it has nothing to do with screen height, either. That would be V2, and really isn't a part of the discussion in this thread.
Feel free to use the word "rotate." It's in common use in the hangar, probably from your instructor, and it's found more than likely in your pilot operating handbook or aircraft flight manual, and most likely in your text book(s) that are used for your basic flying learning and understanding.