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Yesterday (28 June 2016), a Bombardier Q400 from EPGD to EPWA made an emergency landing because of a blown tire, spotted by a passenger. Everything went smoothly and the plane landed successfully assisted by fire trucks.

You can see the article and video here (in Polish).

In addition to the damaged tire, I've spotted that there is some damage to some parts of the plane: photograph of part of plane showing blown tire and some damage to plane body

  • Is it okay to fly with that?
  • I guess it isn't important for the safety of the flight (it looks like some landing gear cover or something), but what damage to the airplane is considered safe for flight?
  • Is it possible to force the airline to repair non-critical parts?
  • I know that loose parts of airplanes could do harm when they fall off, e.g. during takeoff, and stay on the runway (like in the Air France Flight 4590 Concorde crash).
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    $\begingroup$ Hello Mark, welcome to Aviation.SE! $\endgroup$ – DeltaLima Jun 29 '16 at 7:25
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    $\begingroup$ This doesn't answer your question, but to me it seems that the damage to the gear cover was likely caused by the blown tyre. $\endgroup$ – Sanchises Jun 29 '16 at 7:59
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    $\begingroup$ "Is it possible to force the airline to repair non-critical parts?": Any aircraft got parts that are not working (e.g. a thrust reverser). It would cost a lot and wouldn't help safety significantly to have all parts in perfect conditions (the passenger wouldn't understand paying twice the price for something that is very unlikely to cause a problem). To sort between nice to have and mandatory equipment, there is a list of devices that must work before dispatching the flight: The Minimum Equipment List, MEL. $\endgroup$ – mins Jun 29 '16 at 9:32
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    $\begingroup$ Nice list, thank you. But there are mainly cockpit indicators and accessories that are mentioned there. What about external parts, like that landing gear cover? Is it mandatory to have it? $\endgroup$ – Mark Jun 29 '16 at 9:33
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    $\begingroup$ Gears are covered starting page 97 (32-1) of the MEL. MEL is complemented by the Configuration Deviation List (CDL) which lists which parts may be missing and the Aircraft Maintenance Manual (AMM) which describes the degree of damage allowed to the airframe. I cannot find related examples online. Hopefully, someone in the real business may provide additional information. $\endgroup$ – mins Jun 29 '16 at 10:17
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Aircraft Maintenance Engineer here.

To evaluate if an aircraft is safe to fly we use three main reference documents:

1. MEL (minimum equipment list).

This document contains the list of elements that are allowed to be inoperative.

For example a pneumatic valve, a computer, a seat, etc...

All unserviceable elements will have to be fixed within a predetermined duration/limit. (Usually 1, 3, 10 or 120 days)

If the failure is not fixed by the due date, the whole aircraft will not be released to fly. (No matter how small the fault is)

2. CDL (components deviation list).

This document contains the list of components that may be removed from the aircraft.

For example a damaged refueling service door can be removed, if the maintenance team is unable to fix it before departure.

These will usually be associated with performance penalties.

CDL defects will also come with a deadline.

3. SRM (structural repair manual).

This manual contains all information needed to evaluate structural damage such as dents, scratch, lightning strike.

This manual will also give you the information needed to evaluate if a damage is "no-go" (meaning the aircraft is not safe for flight) or if the damage is within tolerance.

If it is within tolerance you will also get time or aircraft cycles limitations (a cycle is a takeoff and landing)

Regarding your picture:

The plane will not be allowed to fly with a blown tyre. A blown/damaged/worn out tyre is a no-go.

However, airliners are designed to land safely with one blown tyre. Aircraft incorporate lots of redundancy so as to eliminate single points of failure — for example, most commercial jetliners are designed to be able to land safely even if they lose an engine. Efficiency, comfort, and ease of operation may be reduced but the situation can be kept under control and is still within the aircraft's design specifications.

I can see damage on the landing gear door. It is possible that an aircraft would be allowed to fly with the landing gear door removed if a fix cannot be performed before departure, however; the aircraft may experience increased drag. This would be covered in the CDL.

The aircraft should also receive extensive inspection before departure and after landing.

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    $\begingroup$ Technically, an airliner can land just fine with all engines unserviceable, as long as it can make it to the runway. :) Climbing out with all engines unserviceable is more of a problem, though. In all seriousness, though, good answer. $\endgroup$ – reirab Jun 29 '16 at 18:47
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    $\begingroup$ Just to add that engine manufacturers - and I assume aircraft manufacturers also - provide a 24/7/365 "technical hotline" service to give professional advice about situations which are not explicitly covered by the documentation and regulations. These days, there is no big problem setting up a live video link between a maintenance engineer on the ground operating a camera, and a technical specialist on the other side of the world. (Some of the in-service issues that arise are truly surreal - but that would be going off topic!) $\endgroup$ – alephzero Jun 29 '16 at 20:50
  • $\begingroup$ So you mean if a seat doesn't recline in coach, and they don't fix it in (let's say) 120 days, the whole plane is grounded? That is harsh! $\endgroup$ – corsiKa Jun 30 '16 at 0:13
  • $\begingroup$ @corsiKa -- yes -- the idea is that the plane will be overnight-or-longer at a main hub/maintenance base and/or receiving a light check (such as an A-check) before that 120day interval is up, giving the mechanics time to fix the busted seat or what-have-you. $\endgroup$ – UnrecognizedFallingObject Jun 30 '16 at 0:35
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    $\begingroup$ You might want to add that no gear leg in todays airliners has less than two wheels purely for redundancy. And yes, the airplane could operate with one of them inoperable, but for far fewer hours and with weight restrictions, so in certain circumstances (fly back empty to repair base) the plane is good to fly with one wheel less. $\endgroup$ – Peter Kämpf Jun 30 '16 at 16:25
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The other answer goes over the MEL/CDL/SRM, but I'll address your specific questions:

Is it okay to fly with that?

(I assume you are talking about the gear door, not the tire) That depends, specifically in this instance I doubt that there would be any issue flying with that small amount of damage considering it is on a gear door on the bottom of the engine pod. I would, as a pilot though, want my maintenance people to look over it for damage you can't see on this side, perhaps rubber flew up into the gear bay and broke/dented a hydraulic line, etc. If it really is as superficial as it looks, it would probably be OK.

I guess it isn't important for the safety of flight (it looks like some landing gear cover or something), but what damage of airplane is considered safe for flight?

Gear doors can tear off and rip through other parts of the fuselage, like the tail, so they can be safety critical if damaged enough. As far as what damage is considered safe for flight it really depends on the damage and its location. Some damage that cannot be seen like JAL Flight 123 which had a damaged aft pressure bulkhead from a hard landing 7 years prior. Hard landings may not have any outward appearance but hide dangerous internal damage.

The only way to find out if its safe to fly is to have it inspected. Only then can it be determined if the damage would render the flight unsafe. I don't know of any pilot that would look out the window, see damage, and determine it was safe to continue. Typically after noticing damage the next thing you do is look for a place to put it down and inspect it.

Is it possible to force the airline to repair non-critical parts?

I'm not sure who you are talking about doing the forcing? If it is you as a passenger, you could simply bring it to the attention of the crew and if you don't have a satisfactory answer, re-book your flight. You could even tell other passengers you don't feel safe due to XXX. Considering how many times I've been delayed because there was an issue with the pilots seat sliders on an ERJ, I'm guessing most times the crew knows about it and maintenance is on its way. However if you notice something, speak up, it may save some lives. Just be discreet (don't scream and yell because you see dirty rivets), crews are pretty good about wanting to make it there alive and will take any concerns seriously.

If you are talking about the airline doing the repair versus the manufacturer, this happens pretty often. Most airlines have maintenance crews for that reason.

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    $\begingroup$ Excellent point about the crew wanting to make it home alive, too. $\endgroup$ – FreeMan Jun 29 '16 at 18:53
  • $\begingroup$ @FreeMan Crew is under financial pressure from the airline so technically they are the least inclined to make it home alive of all people on board (unless a suicidal passenger happens). $\endgroup$ – Agent_L Jun 30 '16 at 12:13
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    $\begingroup$ @Agent_L if you're more concerned with money than making it home to see your spouse, children, parents, pets, whatever, I pray to God that you're never in charge of a passenger flight. Aside from that, I don't see what the company wanting to maximize profit has to do with a pilot's desire to return to earth in one piece. $\endgroup$ – FreeMan Jun 30 '16 at 12:17
  • $\begingroup$ @FreeMan en.wikipedia.org/wiki/2010_Polish_Air_Force_Tu-154_crash Pilots pressured by their superiors into killing everyone on board (pilots, the superiors and nearly hundred of innocent bystanders). $\endgroup$ – Agent_L Jun 30 '16 at 12:19
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    $\begingroup$ @FreeMan It's not "I'll give you $100 more if you kill yourself". It's "Do what we tell you, or you'll have no job to support your spouse, children, parents and pets". I pray to God that you're never in charge of anything if you refuse to admit that people can be pressured into most stupid things. $\endgroup$ – Agent_L Jun 30 '16 at 12:24

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