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The DC-9-80 (marketed as the "MD-80") has, mounted to its nose gear, what I presume to be a debris deflector (a sled-shaped device to keep the nose gear from kicking up pieces of gravel or asphalt or zombie hands that could dent or puncture the fuselage or wings or get sucked into an engine).

This presumed debris deflector seems to extend almost as low as the bottom of the nosewheels themselves:

that looks to be a wee bit on the low side

(Image originally by Anthony92931 at Wikimedia Commons; cropped and annotated by me.)

It seems to me, with a debris deflector mounted that low down, that, upon derotation, the nosegear tyres could easily compress enough for the deflector to strike the runway surface, which would cause it to experience very rapid wear, and could conceivably tear it completely free of the aircraft (thus adding to the debris problem, rather than mitigating it). How is this avoided?

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    $\begingroup$ Out of curiosity, what made you think that the answer would be different from "it is actually high enough"? Is there any particular reason? I don't want to be argumentative or anything, I am just curious. $\endgroup$ Commented Aug 19, 2021 at 12:02
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    $\begingroup$ @VladimirCravero I think the OP wonders whether they are missing something. E.g., is the lower part made of rubber (seems possible looking at the photo in ymb1's answer)? Does it magically move somehow? $\endgroup$ Commented Aug 19, 2021 at 14:00
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    $\begingroup$ If you compress the nose tires enough for that thing to hit you will have broken other parts and rapid wear of the device will be the least of your concerns. Aircraft tires are pretty high pressure and don't have a lot of give to them. (excepting tundra tires on bush planes) $\endgroup$ Commented Aug 19, 2021 at 15:35
  • $\begingroup$ @Peter-ReinstateMonica: She, not they, but yeah, that's pretty much what I was wondering. $\endgroup$
    – Vikki
    Commented Dec 14, 2021 at 23:35
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    $\begingroup$ @Vikki Wow, it's been a while since this comment! Glad to know I had the right hunch here (it looks weird to me as well, as if it should rub on the runway). As an aside: I didn't get the pronoun right though; I didn't look at your profile. I thought "they" covers all genders? Non-native speaker here trying to do the right thing ;-). $\endgroup$ Commented Dec 14, 2021 at 23:51

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FOD/spray deflector
MD-80 (née "DC-9-80") FOD/spray deflector; all rights reserved by Stefan Sjogren

The FOD/spray deflector is attached to the wheels with enough margin for tire compression. Dragging it along in case of dual NLG tire failure is no different than dragging both wheels.

Another view on the MD-90 with hand for scale:

FOD/spray deflector
Source: [1] p. 9; see other MD-80 views: airlinegeeks.com and wikimedia.org

RE comment on material: the inner surface (lining) of the side deflectors is rubber,[1]:13–14 which would be for ease of replacement instead of fixing metal dents.


1: Aircraft Accident Investigation Report KNKT.09.02.05.04 (PDF)

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  • $\begingroup$ Reading that report convinces me that the OP's concerns are valid! It seems that the debris deflector was damaged by some object on the ground, and its subsequent breakage was directly responsible for the accident. $\endgroup$
    – TonyK
    Commented Aug 19, 2021 at 17:27
  • $\begingroup$ @TonyK, damage from hitting another object on the ground is not the same thing as the OP's concern that "the nosegear tyres could easily compress enough for the deflector to strike the runway surface..." As I commented above, if both nose tires have experienced enough trauma to compress by the span of a full hand width, you will have many other problems and damage to concern yourself with. Jet aircraft tires are very high pressure and I would bet money that the entire nose gear strut would break and collapse before the tires would compress enough for that thing to touch the runway. $\endgroup$ Commented Aug 19, 2021 at 20:51
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    $\begingroup$ @MichaelHall: Yes, of course. But it is a small step from the deflector striking the runway surface to the deflector striking a small object on the ground, which is probably what happened. $\endgroup$
    – TonyK
    Commented Aug 19, 2021 at 21:22
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    $\begingroup$ @TonyK, I'm truly not trying to start/continue an argument here, but I respectfully disagree that there is a "small step" between the two; as if there were a progression from one to the other. My point is that we are considering two distinct and separate risks here: One is randomly striking an object on the ground, the others is applying a force, (i.e. hard landing on the nose) sufficient to compress the tires causing this device to contact the runway. One root cause does not lead to the other as I interpret your point to be... $\endgroup$ Commented Aug 20, 2021 at 0:22

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