Porpoising a Mooney

[Yetti]

verb (used without object), por·poised, por·pois·ing.

3. (of a speeding motorboat) to leap clear of the water after striking a wave.
4. (of a torpedo) to appear above the surface of the water.
5. to move forward with a rising and falling motion in the manner of a porpoise: The car has a tendency to porpoise when overloaded.

The standard line is 3 bounce and you will have a prop strike.

What is really going on?   You are no longer flying the plane.

How did you get yourself into this situation?   You let the plane hit the ground too hard and it bounced.  Usually this is because you had too much speed, but you could also misjudged the flare.

How do you get yourself out of this situation?   If you had too much speed, the plane is still flyable.   Hold the nose off,  and you can set up to land if you have more runway.  This is where most people should go around.

Sidenote (you can gently fly the plane onto the runway at 90knots, no flaps)   This is how the Mooney Caravan lands.  If you wack the runway, the plane will bounce back off.  If you gently find the runway the plane will land.  Make sure you have lots of runway or good brakes.

flame away and add your thoughts.

[Hank]

Been there, done that, had no fun . . . . .

Just quit paying attention in the flare, happy to be home as a barely-100-hour pilot coming back from Thanksgiving and finding a surprise college football TFR. Tower guided me around it, bring me across the 3000' runway at midfield, circled around to downwind and went to land. So happy to be home and see the runway lights all working. Funny landing, hey I'm in the air again! Thunk, bounce, what's happening? Full throttle, it's dark, I can't see the trees at the end . . .

Concentrated all the way around, thinking "figure it out later, make a normal landing. figure it out later, make a normal landing" over and over and over. Made a normal landing, pushed into the hangar, unloaded the plane, drove home and went to bed, still thinking about it. Finally figured out much later that I just didn't pay attention in the flare and was either too high or too fast. either or which will cause a nose-low landing and bounce. Yes, the second bounce was higher than the first. No, there was no problem climbing out. No, I could not see the trees in my landing light, because the nose was pointing above them. No, I didn't dig any small branches out of the gear. No idea how close it was, and don't really want to know.

So be on speed when you come in to land. If you are too fast, just hold it off and float a few hundred feet or more [I've since learned that the rule is 100' of extra float for every 1 mph too fast; note that the proper speed is lower for lower landing weights--solo vs. two people, 15 gal vs. full tanks, etc.]. Pay attention and bring the nose up as the plane inches towards the runway, and listen for the stall buzzer at less than 12" agl. It works the same way at night as it does during the day, you just have to pay more attention to judging height above pavement.

Ya'll be careful out there!!

[Hank]

With sufficient runway, it is possible to treat the first porpoise bounce just like a balloon, give it a kiss of throttle to level out then retard the throttle and land again. We've all done this with a balloon. But the porpoise is much more of a surprise, because you already landed once but the plane rejected it for you. So just go around on the second bounce.

[jaylw314]

35 minutes ago, Yetti said:

 

How did you get yourself into this situation?   You let the plane hit the ground too hard and it bounced.  Usually this is because you had too much speed, but you could also misjudged the flare.

Technically, "porpoising" in aviation also requires a landing with improper attitude, with insufficient AOA and the nose too low (see the Aircraft Flying Handbook).  This results in a rapid increase of AOA on contact with the ground.  That is to distinguish it from a "bounce" which is a hard landing but can be with proper attitude.

Realistically, of course, the recovery is the same for both, so how you got there doesn't matter as much as what you do next. 

[jlunseth]

We have discussed this before.  A porpoise occurs when the pilot either lands nose gear first, or lands too flat and lets the nose gear drop by letting go of the yoke.  Either one will cause the rocking nose-main-nose type of bounce, i.e. a porpoise.  It is dumb to do that because it is easily fixed, even when a porpoise has started.  Pick up the nose.  If that results in a balloon you can let the plane down, assuming you have runway left, by giving it a little throttle in the same way you would do a soft field landing, but again, keeping the nose up.

When the nose is up, the plane may bounce on the mains but it will settle down, at least my K does.  But if you fail to control the nose and let the nose get involved in the bouncing, it will be one-two-prop strike!

Land on the mains with the nose up and it may bounce, but it will not porpoise unless you let go of the nose. 

If you don't yet have the skill to pick the nose up and keep it up, then go around on the first bounce. 

[Mooneymite]

And just to be clear, despite the lack of a nose gear, tail draggers are not immune to the phenomenon of porpoising.  It's different in tail draggers, but the underlying causes are the same:  poor speed control.

While is is true that virtually any airplane can be "flown into the ground gently" at extremely high speeds, in my opinion, it is not a "landing", it is something else.  A landing should be on-speed.  Approach at 1.3 Vs, touch down at 1.2, (or less).

In the simulator, I have flown jets onto the ground (gently) at 250 kts, but that is not a landing.  It is an aborted-high-speed-pass at ground level.  

[jaylw314]

48 minutes ago, Mooneymite said:

And just to be clear, despite the lack of a nose gear, tail draggers are not immune to the phenomenon of porpoising.  It's different in tail draggers, but the underlying causes are the same:  poor speed control.

While is is true that virtually any airplane can be "flown into the ground gently" at extremely high speeds, in my opinion, it is not a "landing", it is something else.  A landing should be on-speed.  Approach at 1.3 Vs, touch down at 1.2, (or less).

In the simulator, I have flown jets onto the ground (gently) at 250 kts, but that is not a landing.  It is an aborted-high-speed-pass at ground level.  

I'd say over the numbers at 1.2 Vs is good, but that's still too fast for a good touchdown.  I don't know if I agree that every touchdown should be at a full stall, but when recording my landings, it looks like I routinely touch down around 1.0 Vs.

I'd think most people would say taildraggers are more prone to porpoising, since any significant bounce also causes a sudden increase in AOA.

[Yetti]

1 hour ago, Mooneymite said:

 

In the simulator, I have flown jets onto the ground (gently) at 250 kts, but that is not a landing.  It is an aborted-high-speed-pass at ground level.  

Or SOP for #SWA

[LANCECASPER]

1 hour ago, Yetti said:

Or SOP for #SWA

and part of which keeps Michelin in business .. lol

[MIm20c]

I’ve been on one flight (right seat) that we bounced twice and then had a perfect touchdown. I’ve given it a lot of thought since that time on what went wrong and how I would do it differently in the future. 

Background...

Landing after a 900 nm direct flight

Know icing conditions- flew through a fair amount 1500-2500 agl

First approach to mins (DA) resulted in GA. Broke out in sunny skies right over the airport (very strange weather) 

Back up into icing and set up second approach using MDA.  Set us up for being high and fast when we broke out. Did not bleed off enough speed and did two small bounces that felt like might have turned into a porpoise. Chose to burn up more runway (we had plenty) and hold it off. 

Had about 1.4 hrs of fuel left and conditions were lifting. 

This feels like a “real world” occurrence. What would you do?  I can see it both ways go around vs hold it off. 

[Hank]

Bounce recovery is easy.

Porpoises generally start with a slight nose-wheel-first touchdown, which bounces the plane onto the mains; because excess speed contributed to the nose-low attitude, you are now flying just above the runway, and because the throttle is at idle, you stall and the nose comes down harder, which throws the plane back onto the mains harder, which bounces you higher, so that when you stall the next time you fall farther, the nose drops more, hits harder and bounces you higher . . . . The cycle continues until the nose down angle is steep enough to hit the prop, the impact is hard enough to fold / break the nose gear, or the prop hits. Whatever you as the pilot do to correct the situation is generally out of phase enougn to just make it worse. Go around!

Somewhere there's a video of an Arrow doing this for five or six bounces, each higher than the one before, until the nose gear breaks off and bounces 15-20' into the air as the pavement stops the prop . . . .

[Rick Junkin]

Interesting thread, Yetti.

Here's a trick question - do you fly your airplane with respect to angle of attack or airspeed? And no, it doesn't matter if you have an AoA indicating system.

Without documenting some very embarrassing situations, I'll offer that if you have and maintain control of the airplane (which means the airplane is doing what you are commanding it to do with your power and flight control inputs) and you have enough runway ahead of you, you can achieve the parameters necessary for a successful landing.

Having said that, if a true porpoise situation is developing (nose wheel finding the runway before the mains) the best option for most of us is to see how quickly we can get the throttle to the firewall and give ourselves another chance to get set up for a stabilized approach on the next attempt. I concede that there are many other factors that will run through one's mind (weather, fuel state, ego...) but if you aren't controlling the airplane, nothing good will come of trying to force it onto the runway.

Cheers,
Rick

[kortopates]

The video of the Archer pilot porpoising is in the first post of our recent long thread on the topic

 

[jaylw314]

41 minutes ago, MIm20c said:

Back up into icing and set up second approach using MDA.  Set us up for being high and fast when we broke out. Did not bleed off enough speed and did two small bounces that felt like might have turned into a porpoise. Chose to burn up more runway (we had plenty) and hold it off. 

Were you at MDA for circling or straight in?  If circling, it helps to just plan on circling back to the same runway rather than landing from what could be the MAP at 800' AGL.  It's like flying a low pattern, and you can start your descent from the appropriate time and place, instead of diving from the runway threshold.

[Hank]

16 minutes ago, kortopates said:

The video of the Archer pilot porpoising is in the first post of our recent long thread on the topic.

But, but, but . . . . this is our current thread on the topic, getting longer . . .

Thanks for posting it again! 

Edited September 19, 2018 by Hank

[MIm20c]

27 minutes ago, jaylw314 said:

Were you at MDA for circling or straight in?  If circling, it helps to just plan on circling back to the same runway rather than landing from what could be the MAP at 800' AGL.  It's like flying a low pattern, and you can start your descent from the appropriate time and place, instead of diving from the runway threshold.

Straight in, I did wonder about canceling ifr during the missed as the weather was beautiful around the airport minus the ice covered trees around us. I guess since the circling was the same as the lnav mda we could have circled around the airport and remained in the system  

[jaylw314]

1 hour ago, MIm20c said:

Straight in, I did wonder about canceling ifr during the missed as the weather was beautiful around the airport minus the ice covered trees around us. I guess since the circling was the same as the lnav mda we could have circled around the airport and remained in the system  

Yeah, I can't tell how far the MAP is from the runway threshold, but if it's less than a mile that's a pretty steep dive to the runway.  If the straight-in and circling altitudes are the same, I'd say just plan on circling in that particular situation, but you know what they say about hindsight...

[Yetti]

1 hour ago, Junkman said:

 

Here's a trick question - do you fly your airplane with respect to angle of attack or airspeed? And no, it doesn't matter if you have an AoA indicating system.

 

Neither.   I land using energy management.  At my field I am at the top of the white arc or above abeam the threshold.  If above pull up a little and bleed off speed.   Then throw out the bottom speed brakes (aka gear)   That starts the energy reduction.   The U turn to the runway is going to burn up more energy.   Now I still have flaps for more energy reduction. Based on wind and where everything is lining up go to half flaps at mid point of the U turn.  always fly coordinated, no turns under 90mph without flaps deployed.  If I ever need to add energy, there is a throttle.   If there is a strong headwind, that will dissipate more energy or I can pull up a bit on final to dissipate more energy (never done it, but that is how you dissipate energy skiing, ski uphill).

[Rick Junkin]

13 minutes ago, Yetti said:

 I land using energy management. 

Of course you do. But how do you assess your energy level?

[Yetti]

27 minutes ago, Junkman said:

Of course you do. But how do you assess your energy level?

Same way you do when landing a sailboat at a dock.  Too fast and you smack the dock.  Too little and your bow man gets wet.

[Rick Junkin]

5 minutes ago, Yetti said:

Same way you do when landing a sailboat at a dock.  Too fast and you smack the dock.  Too little and your bow man gets wet.

I was hoping you'd use an appropriate aeronautical analogy, but I'm done asking you questions. 

[Yetti]

Yep I annoyed my flight instructor too when I referred to the sides a port and starboard.  airfoil design and angle of attack when beating up wind in a sail boat are the same as flying/landing an airplane. After all they both have rudders.

[EricJ]

36 minutes ago, Yetti said:

Yep I annoyed my flight instructor too when I referred to the sides a port and starboard.  airfoil design and angle of attack when beating up wind in a sail boat are the same as flying/landing an airplane. After all they both have rudders.

Oddly enough, slip angles on tires during racing are similar to angle of attack on an airfoil, enough so that if the car is pushing out on a corner when the front tires are on the back side of the slip angle curve (i.e., too much angle of attack), you can *increase* the rate of turn by decreasing the input angle of the steering wheel.   Like dropping the nose to fly higher, it is initially counter-intuitive.   I love stuff like that.

[jlunseth]

2 hours ago, Yetti said:

Same way you do when landing a sailboat at a dock.  Too fast and you smack the dock.  Too little and your bow man gets wet.

Well, on our sailboat I just reverse the engine instead of smacking the dock.

[Yetti]

spent my youth racing one design sailboats.  No engines.  not even on Olympic class three man Solings.  You would think that anyone could land a sailboat with an engine, but I have seen that fubared too.