wrf2e

I work for eagle at BNA and today before my shift started I was sitting in ops while they were having a problem with the weight of a CRJ 700. The plane was loaded above the MTOW and we were going to have to take some pax off to to get it back under max. We were over by about 850 lbs. Then the Capt. notices the enroute fuel burn in the release was less than the number he had (the release was under by about 2000 lbs). When we got the new release from dispatch and changed the burn in the W&B software, we had somehow magically dropped under the MTOW.

The ops agent and myself are both commercial pilots with 250hrs a piece but we couldn't figure this out. If you are over the MTOW it seems to me that you would either have to reduce the weight by taking off bags people or fuel, or increase the taxi burn...right? We just couldn't understand how the enroute fuel burn has anything to do with the MTOW.

Thanks for the help in advance.

Roost

Some times the MTOW is based on the MLW + Burn so if the Burn went up then the MTOW went up as well.

wrf2e

That makes alot of sence. I was thinking that the MTOW was set for each AC and didn't change. Thanks for the help....I can go to sleep now

Roost

MTOW can be determined by either Structure, Performance, or Landing weights.

wrf2e

I learn something new everyday. I just called the ops agent to tell him your answer. He said we should have known that but now we do.

Mason32

That's why the he/she is the Capt.

__________________
Fly The Contract & Nothing More

joepilot

In aircraft without a fuel dump system, MTOW is sometimes based on max engine out enroute weight when flying over high terrain. This definitely came into play on the older 737s.

StillLearning

Reference 121.639 and 121.647 and assume an aircraft with the following simplified limits:
max zero fuel weight 95,000
max landing weight 100,000
max takeoff weight 130,000

scenario1:
basic operating weight (BOW): 70,000
payload (passengers and cargo): 21,000
zero fuel weight is 91,000

fuel burn reserve holding taxi extra minimum planned fuel
20,000 10,000 0 1000 0 30,000 31,000

takeoff weight 121,000 (after taxi fuel consumed)
landing weight 101,000 * (after fuel burn)
* 1,000 pounds overweight for landing

Can't go like this, captain is correct to ask for 1,000 pounds of payload to be removed.

scenario2:

If (thru different cruise altitude, route or winds) the fuel burn is revised to 22,000,
you would have to revise your fuel planning to at least:

fuel burn reserve holding taxi extra minimum planned fuel
22,000 10,000 0 1000 0 32,000 33,000

You would still end up 1,000 too heavy for landing, you have to reduce payload prior to departure.

It's easy to fall into the trap of busting 121.639 and 121.647 by increasing the fuel burn to make landing weight without adjusting payload.

No big deal in this Eagle case, if their op specs allow fuel planning from the collins fms, or the original release dispatch performance was in error.

joepilot

The only way this scenario works (increase planned burn to get legal takeoff weight) is if you can at the same time reduce the planned reserves. You might plan a closer alternate, reduce planned hold fuel, eliminate extra, etc. Some places prefuel the plane the night before, based on historical data, or just a guess. In these cases the reserves might well not have been figured correctly. In any case it is always the responsibility of the Captain and the dispatcher to ensure that the fuel load is both safe, according to their best judgement, and legal IAW the FARs.