For reasons that elude, this week’s video has sparked a veritable pandemic (sorry) of questions, suggestions and entreaties about shutting down the engine if a gear-up landing is unavoidable. This didn’t come up when I published the last gear-up video two years ago, but I addressed it then. Will again now.
In this week’s video, I did address the oft-stated fear that a spinning prop will shatter when striking the runway, hurling deadly shrapnel into the cockpit and shredding the hapless occupants. If this has ever happened in the history of manned flight, I’m unaware of it. (Go ahead, change my mind.)
You know why. Metal props are made of soft aluminum which bends like butter when it hits concrete or asphalt. If you’ve ever seen the witness marks a spinning prop leaves on a runway surface, you know that they’re not a series of little craters—or even one crater—but a series of angled striations that trace the physics of the impact. The prop tip speed is about seven times greater than its forward speed through the air, but there is forward speed and it’s enough to impart a bending moment that curls the tips back. But they don’t break off.
What about a prop strike from a stationary position? I once saw a tug roll into one—well, I saw the aftermath—and the prop was similarly bent, but the radius of the curl was larger. Probably if I canvassed prop shops, I could find some sheared parts, but none of them from gear-up landings, I’ll wager.
Composite props are a different matter. Most of them are wood cores covered in laminated composite. These do shatter and hurl bits of wood and plastic circumferentially away from the prop. Cabin penetration? Seems remote, at best.
Now, to the main event: Shutting down the engine to save it from the horrors of a teardown inspection your insurance company will pay for. Or to show what a steely eyed missile man you are behind the stick. I have done this experiment and you could, too, although it does involve some risk.
I was instructing a pilot in his Mooney 201 and the discussion turned to air starts and glide ratio with the engine shut down. One thing led to another and so we climbed 5000 feet over Waterbury-Oxford Airport in Connecticut and shut the engine down. It was a Lycoming IO-360. A couple of things were surprising about this. One is how much effort it took to get the prop stopped and the other was how much effort it took to keep it stopped.
We had to extend flaps and gear and get the airplane almost to a stall to stop the prop. Having done that, cleaning up the airplane and accelerating to best glide got it spinning again. If I were trying to save the prop, I’d have to get the prop stopped, fly a slow approach to keep it stopped and maybe bump it with the starter to align it out of harm’s way. Bumping it might get it spinning again. This may vary from airplane to airplane, but it convinced me I don’t want to mess with it while I am, by the way, trying to plan for aluminum-scraping runway slide. I kinda like to have the option of a go around.
Now the economics of the teardown and inspection. And by the way, whether the engine is running or not, both Lycoming and Continental recommend a teardown after a prop strike. The insurance company, of course, pays for all of this and there’s bit of a tense dance between the shop, the owner and the insurer over what exactly gets paid. It varies. But if nothing is found broken, the engine is reassembled with new gaskets and seals and whatever else needs to be replaced and you’re back in business. You probably get a new prop, new antennas, plus all the sheet metal work and paint. Sometimes, it’s surprisingly little sheet metal work.
Last time I checked, a gear-up landing in a single-engine airplane was averaging around $50,000, but that was quite some time ago. Depending on how you’re insured, it could be a write-off. Take your check. Be happy.
Where it gets interesting is if the engine is close to being run out. Insurance companies don’t like to pay for what they call “betterment,” which means they aren’t going to pay for something that will make you more whole than you were before the slide commenced.
But if the engine needs an overhaul, the insurer is on the hook for the basic breakdown and reassembly, plus whatever parts are necessary for that work. If you upgrade with new cylinders, a cam or whatever, on your own dime, you’re still getting a deeply discounted overhaul. Measure that against however risky you think it is to screw around trying to stop the engine. For me, it’s a no-brainer. I’ll keep the engine running.
There is one argument for shutting it down and trying to keep the prop from striking. If the insurance company deems that no prop strike means no teardown—and there’s no guarantee they will—you won’t have the two-month delay of having the engine done. But the airplane will still need repairs and that may take at least that long.
Nobody said aeronautical decision making is easy.
Of course you two turkeys didn’t manage to shut down the prop turning in flight because you did it wrong.
To shut down the prop in flight the throttle has to be all the way in!!
Again throttle all the way in, you want the cylinders full of air to compress, throttle all the way out is vacuum in the cylinders.
Did the light bulb got on, in your head!! ?
Max M.
You seem very sure of yourself so you may be right. It makes sense but I sure don’t know. However, you might try to convey said information without being so insulting.
Color me amused. Think about this. If the engine happens to stop right on the power stroke for one cylinder, those valves will all be closed. But the valves in the three other cylinders will be in various stages of opening, so the cylinder pressure will be vented to atmospheric ambient. To remain stopped, the engine has to overcome compression in one cylinder because any of the valves cracked open won’t produce compression.
The much larger effect is pulling the prop control to coarse pitch, lessening the drag the prop represents and giving it less leverage to turn the engine. Peter Garrison of Flying once did this test and did find some advantage for both coarse pitch and open throttle. But he wasn’t convinced the data was solid. Absent an instrumented test, neither am I.
https://www.flyingmag.com/gliding-props-and-arithmetic/
“Would you talk like that if it was a group of us sitting around having coffee?”
Yes, and no one would get bent out of shape. If you were a pilot you would know that we are a tough crowd. Anyway the crowd that I hang around with always is, and it is a delight to poke them a bit they sure do it to me. It is called tough men being tough. I do keep in mind that in certain places like in the US Senate you may not want to be rough around the edges they have tremendous and fragile egos.
And
It is all in humor.
I think they should have known that. For example the other comment right after yours is also amusing.
The commenter thinks about one cylinder,, however if thinking in terms of time, all cylinders compress in sequence, all cylinders extract energy from the relative wind and all cylinders are braking.
Tough crowd or not, Max, we have different rules on this forum. You’re welcome to comment, but when I get complaints from readers about the tone of messages, I’m compelled to delete them. That includes name calling, even though you might intend it in jest.
You aimed this one at me and I have a pretty thick skin. But I’m just letting you know that one was right on the edge.
Paul Bertorelli
Why do so many people leave nasty and uncivil comments? Would you talk like that if it was a group of us sitting around having coffee?
Don’t look now Max, but there might be some kids playing on your lawn.
“Again throttle all the way in, you want the cylinders full of air to compress”
That’s the funniest thing I’ve heard all year!
I can conclude with certainty that you’ve never lost an engine with a fix pitched prop.
Look up Otto von Guericke before saying that a vacuum in a vessel is weak.
I know it’s off the subject, but all the Mooneys I had flown had a manual gear
lever.
Just wondering what happened with the one in the photo. (was it electric with no manual backup?)
I don’t know, sorry.
I loved our Johnson-bar Mooney. Sigh…
I don’t want to reveal anything that might identify the participants in this event, but many, many years ago I visited the site, several hours after it happened, of a gear-up landing in which a significant portion of a blade from a Hamilton Standard prop, which had recently been attached to an R2800 engine was found in a baggage compartment, forward of the passenger compartment. The pilot, after realizing that his wheels were still up, slammed full power up just as the plane was about to make asphalt contact. Not only was the right propeller dismembered, the entire nose cases – yes, both engines – were torqued, twisted and sheared off the power sections. Fortunately, the timing of the power application was just right and airplane skidded to a stop before the end of the asphalt, instead of flying a bit further, and everyone got out without anything but memories. This was a rare exception to the probability that a metal prop blade will only bend and twist but not become fragmented. And, I know, this event is not exactly the same thing as the author was addressing.
A few years prior to that event, I observed, from the ground, a popular, low-wing light twin make a successful go-around when the pilot likewise applied full power when he realized his wheels were still up. A post-landing walk-around, after that successful go-around was followed by a successful landing – with the gear down, revealed all prop blade tips on both props were bent approximately 90 degrees. (That was before the revolutionary Q-tip prop blade design.) Also, the trailing edges of the inboard ends of both flaps had been ground off a couple of inches. The only metal that departed the aircraft was from the flaps. One of the closest encounters known to general aviation.
But, apart from all that excitement, it is my opinion that a pilot should retain all the control capability that he would normally have; not try to be heroic and do last-minute, unproven, untrained and unpracticed “tricks” with engines/props. The outcome of an event is most likely to be better if a pilot keeps things as normal as possible, for as long as possible. It’s that “predictable outcome” idea. That includes landing on the hard surface runway, as opposed to the “softer” grass alongside. Even if only one or two of the three are down and locked, (and none can be retracted) keep normal control right down to the touchdown, even though the outcome after that is less predictable.
Just a question — would some argue for shutting engine down & closing off fuel to eliminate any risk of fire? A belly landing should not be an issue, but if perchance you slid off the runway and impacted runway lights or ILS apparatus, you could break open a wing tank etc. Any thoughts for fire mitigation as a last reason to shut the engine down here?
I know this is not related to gear up landings, but your comment about getting the prop stopped reminded me of my primary training. It was in the late 80s. We flew out of N51 in N/E PA in an old C150. The instructor was an old crusty and scary type that had little patience for ineptitude. We would land and he would pop open the window and light up a cheroot. You know the type. Anyway, one of his lessons was circling above the airport and shutting off the engine. We would then pull up the nose to stop the prop. I am here to tell you it was almost vertical. Once it was stopped, he had me lower the nose enough have the prop rotate a certain number of blades. We did this while descending around the airport. He let me know in no uncertain words or methods if the number of blades that rotated was incorrect. once in the pattern, the mixture went in and we had power again. Ultimately, we did this enough times where I could land the plane with the prop stopped.
While unconventional, it taught me airspeed control and managing it in order to make the field. It also showed me how high the nose had to be before the prop stopped. I can’t see how anyone could do that with everything else going in a gear up landing.
“Nobody said aeronautical decision making is easy.” I thought adm was all about flying, including oopsies. If I forget to lower the gear and continue to land oblivious to a gear up landing, that’s all the adm I’m required to know because “I forgot”. If I know I’m landing gear up, isn’t adm still in play when scenarios were discussed in the list of what ifs? And besides, the little helis I trained in all had fixed landing skids so the biggest problem was learning how to take off and land on the portable pads. Oh and I had to understand roll over tendencies if a skid got stuck from an uneven landing…….So many adms to remember.
Aprapos of nothing ,
I beseech you to collaborate in both the written format and especially with video with :
Dan Gryder
http://www.TheAviatorNetwork.com.
Hes kinda famous on you tube with “ Flight Chops “. His latest work is preventing GA loss of conrol fatalities after one of his students crashed and died.
I would pay money to have you Aviators writ large , to do some Videos together.
Very Respectfully ,
Mike