MEL Compliance

[F9DXER]

When an MEL is added the crew are required to abide by the restrictions of said MEL. Yet what if you know that the crew has no control over whether they can abide by said MEL, do you as the dispatcher add it or refuse to issue the release?

Yes that may seem a bit odd but let me explain.

In at least one Boeing type aircraft, the aircraft is designed to automatically determine whether to use VHF, SATCOM or HF for data transmissions. The software is programmed to look in that order as well. So if datalink is being used (which it always is), the crew has no idea which system is being used for data transmissions. Now an MEL is added that states HF datalink is deferred and unusable. Yet it is only on one HF unit, but there is no separate MEL number for HF1 or HF2, just for both. Thus both are considered not useable per the MEL.

Now here is the dilemma, the crew cannot control what the aircraft does, so would/could a violation occur?

Now you may ask why not just defer the faulty HF. Well, if I remember correctly, you cannot defer a working unit, since the HF works for voice communication. Correct me if I am wrong.

Any thoughts?

 

[QXDX]

What does the maintenance action say? I imagine that circuit breakers would be pulled and collared.

 

[Cherokee_Cruiser]

If it’s broken and deferred, how is HF going to transmit data?

I checked our Boeing shop’s MEL, we have one MEL for single INOP and another for both INOP. Neither have any crew action except to ensure the route doesn’t require HF. OAK Oceanic routes require 2, some cases extended overwater across Gulf of Mexico may require 1.

 

[F9DXER]

Mx could have pulled and collard the breaker on one of the HF units, but again. I believe a working system cannot be deferred.

The HF's were not inop, just that one of them could not be used for data transmissions but useable for voice. The MEL to defer datalink is not broken into 2, just one MEL for both units.

 

[Screaming_Emu]

I can’t speak for all Boeings, but on the 747 the airplane will only attempt to use ACARS via VHF or HF if we tune one of the radios all the way to the top/bottom of the scale and that specific radio says ACARS.

For example, Fukuoka FIR wants us to disable HF data when using CPDLC in their airspace. As we reach he FIR boundary we pull up both HF radios and make sure there is some frequency in them other than ACARS. We then get a memo message on the EICAS that says “HF DATA OFF”

 

[Burrito]

What does the maintenance action say? I imagine that circuit breakers would be pulled and collared.

Furthermaybe a lot of what-if-ing, but this is all part of what floats around for me):

Did it pop in-flight? Is it something that would warrant a diversion (i should think one HF doesn't, but. MEL wordings.) Also, I did note Oceanic in an earlier post, and correct me if I'm wrong on this, but doesn't SATCOM -HAVE- to work if only one HF is operable? Before even getting in to the dirty parts of rerouting and fuel planning?

 

[Green12324]

I personally don't see an issue with this MEL the way I'm understanding it. It wouldn't be a violation for HF datalink to happen to work using HF2 while en-route; the MEL just requires that we plan for it not to work.

 

[Jaketheman]

I personally don't see an issue with this MEL the way I'm understanding it. It wouldn't be a violation for HF datalink to happen to work using HF2 while en-route; the MEL just requires that we plan for it not to work.

Exactly what Green12324 said! Too many dispatchers overthink dispatching.

 

[A1TAPE]

Could we say YES we will take the MEL but the plane is restricted to DOMESTIC only routing or swap it out? Like if its doing INTL legs we could say NO its only doing TRANCONs or if we have a working plane we can swap the INTL legs onto that until the MEL expires or you fix it at a MX base.

 

[McCrosky]

We have handy dandy notes in our MEL that specifies any mode that is operative can still be used.

So, if your HFDL has a 2 installed 0 required and one still works. Bobs your uncle, have a nice day! If both HFDL are on the fritz, they should either be 2 deferrals (one for left and one for right), or the deferral should note BOTH inop(depending how your airline does things). Change your alphabet soup in the filing to indicate no HFDL, ensure it’s not required, and go about your day (we actually have it broken down for if 1 inop verses both) the software (I’d expect) wouldn’t use the HF option, cause it won’t work. If it’s trying to ping a station and does cycle to the HF and doesn’t get a ping response, it should keep cycling.if it does get a response then the mode is operative and can be used.

I think if any federalie tried to violate a crew for the software cycling that person is being a Richardhead. The FAA should be aware how the system works, and the limitations available to the flight crews. If not then they’ve been promoted beyond their abilities. If causes a problem then time to go back to the manufacturer and say fix it. I can’t imagine anyone from the CMO picking this to be their hill to die on.

Exactly what Green12324 said! Too many dispatchers overthink dispatching.

Yes! I’m just trying to remember to put ETOPS alternates on my Hawaii flights!

 

[pljenkins]

Specifically to your point, if the MEL is complied with in this instance and the M items accomplished, I am not going to ask those questions. It's up to maintenance and the flight crew to comply with the provisions in the MEL. There are no dispatch actions that I am aware of on the 737NG or MAX relating to HF deferrals. Our MEL is pretty easy for HF deferrals. Placard the offending unit, don't dispatch ETOPS, have a nice flight, seeyabye.

Generally speaking, if I am aware of a situation where it is impossible to legally operate the aircraft with a given MEL, I will refuse the flight until such conditions no longer exist. Icing conditions with a non-ice airplane is a good example.