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When is an aircraft considered to be dispatched?

Before an aircraft is dispatched certain pieces of equipment must be operational on an aircraft. If some equipment is found to be inoperative, a determination can be made of whether or not to dispatch based on the information found in the MEL or CDL.

After an aircraft has been dispatched, disposition of inoperative equipment would follow the guidance inside the AFM.

Simply put, at what point does the dispatcher / crew switch over from relying on the MEL / CDL to the AFM for guidance? The pilot in command has the final authority to takeoff so I am not asking about equipment that are significant to the operation of the airplane.

I am interested in both FAA Part 121 airline operations, Part 135 charter operations and Part 91 flights.

Thanks

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  • $\begingroup$ Good question, I'm interested in seeing if there is a CFR definition. Just a comment though, while I have heard "dispatch" used as a verb, I don't recall hearing it in the past tense this way. In my 135 operations we use the word "released" in this context, and the release comes in the form of a piece of paper faxed by the dispatcher. With this in hand I would consider myself "dispatched". $\endgroup$ Aug 22 '20 at 21:20
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Technically, before the aircraft is dispatched / released, everything can be inoperative.

However, most everything needs to be in working order to be dispatched / released, with exceptions as per the MEL / CDL.

MEL / CDL procedures are followed until the takeoff is commenced.

If an item is discovered to be missing or inoperative,

A) prior to door close

B) after door closed but prior to block out

C) after block out but prior to flight

there are specific MEL procedures to follow in each of those three scenarios.

Taking the runway and setting takeoff thrust / power is the act of commencing a takeoff.

After that point, equipment failures are treated as an in flight emergency, and flight crew follow QRH / AFM guidance. At that point the MEL no longer applies.

Applicable US FARs for Airline ops: 121.687 Dispatch Release - Flag or Domestic Operations 121.689 Flight Release - Supplemental Operations

135 has a similar regulation. 91k (fractional) does as well. Plain Jane 91 owners/operators/pilots don't normally operate with an MEL. If they do, they have a letter of authorization with the FAA.

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  • $\begingroup$ All turbine powered airplanes and airplanes with a MTOW above 12,500 lbs require a MEL. Quite a few corporations have their own flight departments that operate strictly Part 91. $\endgroup$
    – wbeard52
    Aug 23 '20 at 1:09
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Whether you are flying part 121, 135 or 91, the crew, usually the captain, upon arrival in the cockpit, will go through the tech log to make sure all reported defects have been repaired or deferred according to the MEL. They will also conduct a preflight inspection according to the AFM and company SOP, to make sure everything is in order. If further defects are found (let's say the DME isn't working), they will consult the MEL to establish whether they can dispatch, or whether it must be repaired before departure. There might be aeronautical constraints too depending on the nature of the flight (VFR or IFR, type of airspace which might require certain equipment). Look up P-RNAV and B-RNAV. Below is part of the P-RNAV and B-RNAV checklist for educational purposes. If any of those things are not present, you have to fix them or make sure you can dispatch without them.

  • B-RNAV (RNP-5) Aircraft certified for B-RNAV operations at ± 5.0 NM

  • Aircraft authorized B-RNAV in LOA or Ops Spec P-RNAV (RNP-1) Aircraft certified for P-RNAV operations at ± 1.0 NM

  • Aircraft authorized P-RNAV in LOA or Ops Spec

  • Pilot(s) trained and authorized for P-RNAV

  • Aircraft Certification requires state of registry authorization per TGL-10 for both B-RNAV (RNP-5) and P-RNAV (RNP-1)

  • Approved equipment

  • Approved navigational database

  • Approved MEL

  • Operational Approval requires Standard Operating Procedures for Normal operations

  • Contingency operations

  • Incident reporting

  • Flight crew training for P-RNAV (RNP-1) operations PREFLIGHT PLANNING

  • Confirm availability of necessary ground-based navigational aids (NOTAMS)

  • Confirm RAIM availability for GPS based RNAV systems

  • Determine need for dual P-RNAV (RNP-1)

          • For procedures below minimum obstacle clearance altitude
          • When no radar monitor is available for the approach
    

Here are the FAA rules (14 CFR - Part 121) regarding dispatch to service.

There doesn't appear to be a requirement for a dispatcher for part 135 or part 91.

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  • $\begingroup$ That's a very thorough and informative answer as to what is required prior to dispatch, but it doesn't address the root question. Is it issuance of the release form I mentioned in my comment to the OP? (Or an electronic version for aircraft capable of this?) $\endgroup$ Aug 22 '20 at 21:45

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