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I'm imagining if you had a panicky passenger sitting in the right seat who had both feet firmly on the brakes while landing. Unless you had a crosswind and needed rudder as you touched down it's possible you wouldn't be aware of it. Or if there was a malfunction causing them to be locked. How likely is it that could cause you to have a bad day?

What if only one side was locked up (which seems worse to me)?

I'm mainly asking about small aircraft. Would it be any different for an airliner?

What if you were aware of it? What action would you take?

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    $\begingroup$ If parking brakes were left on for an MD-11, this happens. Something to watch until you get an answer :) $\endgroup$ – ymb1 Aug 26 '16 at 21:59
  • $\begingroup$ @ymb1 That's one of the more annoying warning alarms I've ever heard $\endgroup$ – TomMcW Aug 26 '16 at 22:04
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It's mostly harmless in a nose wheel configuration. You quickly blow all tires and slide along the runway on your wheel hubs until the aircraft comes to a rest. Crosswind will make the experience worse, because at lower speed you have less rudder authority and the aircraft might leave the runway.

If only one side is locked you will risk a ground loop. Here it is best to step on the other brake so both cause the same braking force.

But this is peanuts when compared to a tailwheel configuration. Here the consequence is a headstand right after you put some load on the wheels, which can be right at touchdown when you come down with some sink speed. Depending on the speed of the aircraft when this happens and the length of the fuselage nose, the aircraft might even flip on its back. Now this is sure to ruin your day. I've witnessed this once with a Polish Yak-12 which landed on soft ground - nothing more. The pilot climbed out unhurt from his inverted position, but damage to the aircraft was extensive. This was the occasion when I learned the worst Polish cursing ever.

If only one side is locked in case of a taildragger, I am unsure what will happen first: Ground loop or headstand. Details depend on the wheel track and the attitude at touchdown. Be sure to touchdown at the lowest possible speed and with the highest nose-up incidence possible to increase the resistance of the aircraft against flippig over. Unload the locked wheel with ailerons, so you touch down on the working wheel only, but make sure that you do this with as little sideslip angle as possible. Flying a gentle turn while touching down will help - just place the touchdown point at the moment when the aircraft is aligned with the runway (I know - easier said than done).

Touching down on one main wheel of a taildragger with some lateral speed by sideslipping into the direction of the working wheel will quickly roll the aircraft into the direction of the lateral speed, which helps to unload the locked wheel but might end up in a three-point landing: One wheel, wingtip and fuselage nose. Again, this is sure to ruin your day.

TBM-3U after having landed on wheels and nose That is what is colloquially called a "headstand" (Picture source)

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  • $\begingroup$ For a really big headstand, see: neopress.in/… $\endgroup$ – WBT Aug 27 '16 at 17:07
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I've seen it happen many times (ask any rental place about this). You get a big bald spot cut into the tread. Sometimes it goes all the way through the tire.

If it happened on one side, you'd likely get a ground loop.

Pair of tiles with flat spots and holes

Tire with flat spot

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  • $\begingroup$ So, costly, but not necessarily catastrophic $\endgroup$ – TomMcW Aug 26 '16 at 22:25
  • $\begingroup$ Depends on the skill of the pilot, if you are touching down firmly in a cross wind with the upwind tire first, it could be very catastrophic. Usually you can tell if the passenger has their feet on the pedals, which would mean go around and a lecture from me. My preflight safety briefing includes telling the passenger to stay off the pedals. $\endgroup$ – Ron Beyer Aug 26 '16 at 22:27
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When Air Transat Flight 326 glided into the Azores after fuel exhaustion over the Atlantic, the pilots were unsure whether they would be able to apply the brakes on their Airbus 330 more than once, and their anti-skid systems were inoperative. So they applied the brakes and held them, locking the wheels. The results, from the accident report:

The tires quickly abraded and deflated at a point between about 300 and 450 feet beyond the second and final touch down. The segments of the main wheels contacting the pavement were worn down to the bearing journals, the left, rear, inboard wheel detached from the axle. Both left and right brake anti-torque links attachment horns on the bottom segments of the main oleos also contacted the pavement; the horns were abraded to the point that some of the links separated from the oleo resulting in the rotation of at least one brake carrier. Shedding of brake and wheel components during the landing run also resulted in a combination of punctures and impact damage to the airframe and left engine nacelle.

...

CFR [Crash Fire Rescue] reported that there was fire visible coming from the main wheels, and responded to put out the fire. At 06:46, CFR reported that the evacuation was in progress and that some signs of fire still existed in the left main wheels. By 06:54, all fires were extinguished; the areas around the main wheels continued to be monitored due to the fire hazard associated with the damaged wheels and hot brakes.

enter image description here

However, the airline stayed on the runway, and everyone survived. (Two passengers were hospitalized due to their injuries.)

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If that happens to an airliner(full brakes at touchdown), a lot can happen. 1- depending on the landing speed, the wheel struts could break off 2- if the struts resist such enormous load and bending force, the n the wheels will wear and burst due to friction and then most certainly burn depending on the condition of the runway(wet or dry).

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    $\begingroup$ A locked wheel causes less horizontal load than one with full brakes which is still rotating, thanks to an anti-skid system. The legs will only break off in a Hollywood movie or when the aircraft hits an obstacle at high speed. $\endgroup$ – Peter Kämpf Aug 29 '16 at 20:43
  • $\begingroup$ @PeterKämpf that's true, locked wheels don't brake as well as rolling ones. $\endgroup$ – Harper Sep 14 at 22:48

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