Aborted take off due to not closed cargo doors. How this will be signalled?

Question

A hypothetical situation (I know that it is very unlikely to happen in real). When closing cargo doors, a piece of fabric from the luggage carrier's uniform stick in between. The cargo door is actually closed (no real danger), but the latching sensors are sending a misleading signals.

How this will be communicated in the cockpit? What visual or audio signal will be used / emitted in the cockpit to inform the crew about the reason? Is there any specific light or button as an endpoint for cargo doors sensor? Is there any specific sound?

How will the crew communicate to the tower the reason for an aborted take off (what kind of message, who will do this -- flying pilot, non-flying pilot)?

Clarification: This question is for the sake of the story that I am writing. It (both story and the question) involves Boeing 777 taking off from LHR in August 2014.

Aborted take of is due to a misleading information coming from cargo doors' sensors that reveal a possible problem only during take-off, not before (i.e. during taxi). The doors are actually closed (no real danger posed after check). But there's a tiny piece of fabrics from cargo loader's uniform stick in between doors. This question is a follow-up or alternate version of this question. Here I'd like to know what happens, if such situation will be detected before V1. In linked question I am asking about the same situation detected after V1 or shortly after take-off and thus after such aircraft returns safely to the airport and clears the runway.

I am aware that most airline experts will say that such situation is not possible at all. I am, on the other hand, a system designer and I know that such "ghost" situations of "neither 0 nor 1" sometimes do happen. But, for the sake of this question, if you feel uncomfortable with such reason -- let's assume that take-off was aborted due to any other reason, i.e. engine failure. I belive that such reason has similar severity as the need of checking whether cargo doors are really closed due to fact that on-board computer provides misleading data.

I'd lilke to underline that this is purely hypothetical question. I am aware that while such questions are sometimes hard to answer, they're in general quite welcomed in this site and are not off-topic.

Answer 1

You will typically get a DOOR OPEN alert displayed on the EICAS system. A competent crew would have spotted such a discrepancy before pushback.

Answer 2

It's possible for an indication to appear after the fact; in other words, what wasn't evident prior to pushback and engine start, becomes evident at a later time. During the takeoff roll, for example. I can't recall ever rejecting a takeoff for something I knew about before entering the runway: it's something that occurs later.

A piece of fabric in a cargo door wouldn't cause the door to fail, though conceivably it might be possible for an erroneous indication to develop. Or at least it's plausible enough to be included in a story. There's certainly far less credible ideas, such as the movie Airport, in which an airliner submerged under the ocean is still producing bleed air from it's flooded engines to pressurize the airplane...or the ubiquitous (and idiotic) trope about airplanes that blow apart when someone fires a shot inside.

For the sake of argument, say that the fabric does cause an error in the door closed indication after the takeoff has begun, is discovered prior to 80 knots, and the takeoff rejected. The crew may report the reason to air traffic control, but realistically will be notifying ATC that there's a mechanical cause and will be requesting a return to the gate. The immediate problem may be that the gate is no longer available, if it's been arranged for another flight. In any event, even with the discovery of fabric, the airline maintenance will not make the assumption that the cause has been discovered, and will inspect the door and door system for other problems.

I had an instance in a much smaller airplane many years ago, in a Learjet 35A, departing Los Angeles (LAX). A very new captain was in the left seat, and I was in the right. Passing 80 knots, I got a door light (the cabin entrance door on the Lear is large and could be very dangerous if opening). I announced the door light and called for the reject. The new captain didn't respond.

I knew the door system well enough to glance over my shoulder, note the handle position, and knew that the door couldn't open. I knew that the sensor for the door was in the handle, sometimes not depressing the microswitch due to interior trim interference. Short story: I knew the door had to be closed and couldn't open. I also didn't intend to put the flight in jeopardy by attempting to reject or take the airplane from the other pilot...who was clearly zoned out and too focused on the takeoff to hear or respond.

I called V1, rotate, and after we left the ground, positive climb. When the new captain didn't respond, I announced the gear, raised it, and walked the airplane through the takeoff flows, and clean-up. The captain was still focused and not listening. When I was done with the checklist, I pointed to the door light and said firmly, "You're aware of the door light?"

For the first time, the captain responded, and to be polite, he freaked out, and attempted a rapid bank. I took the aircraft from him, and asked what he intended to do. He said he was going to return to land opposite direction at LAX...bad idea. I told him we would not, and that we'd continue the departure until above 18,000, when I'd check the door. I informed him that it was a sensor, that I knew it was a sensor, and that we weren't going to create an emergency over a sensor (the Lear door can't open with the handle forward). When we were up and clear, I pulled the door trim aside, and pressed the handle down, an the light went out. We reviewed the checklist, and continued.

A high speed rejected takeoff is one of the most dangerous things you can do in a transport category turbojet aircraft.