Level Busts?

[AH64 APACHE]

Can someone tell me what these are?
Do they exist?

[Engineer]

Yes they do and it is when an aircraft is cleared to a specified level and fails to level off at that FL or altitude within + or - 200ft oops


[This message has been edited by Engineer (edited 24 March 2001).]

[AMEX]

A cleared level is within 200 feet (+ OR - 200').

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If you can't save the engine...save the airframe :D

[shakespeare]

The B747-200 and BAe 146 a/c are the two most common culprits of this "phenomenom". The 146 in particular has an AFGS system which allows the pilot to DISARM the selected altitude whether in manual or auto-pilot flight, by pushing or switching certain buttons, toggles etc when the a/c is in the "FLARE" mode. The newer RJ a/c have dealt with this problem!

It is very dangerous to the inexperienced 146 pilot who does not fully understand and/or comprehend the system.

[AssumeCrashPositions]

I just searched for this topic and this thread came up. I have to do a presentation for a bmi sponsorship and the topic is level busts - can anyone point me in the right direction as regards statistics, reasons why they occur, etc. I'm looking to go into as much detail as possible so any info, no matter how small, would be very much appreciated.

Also, can anybody tell me if pilots have to dial 1013mb into the computer when going through the transition altitude or does the FMC already know and adjust the QNH automatically? What I'm trying to get at is, could the pilot of a modern jet simply forget to do this or are there warning signals or something?

Any help would be brilliant. Thanks in advance.

Andrew.

[Gonzo]

ACP,

CAA/SRG have been publicising a campaign over the last year or so about level busts, so maybe try their website. www.nats.co.uk (http://www.nats.co.uk) and www.atmdc.nats.co.uk (http://www.atmdc.nats.co.uk) may have some more info!

Gonzo

[Speedbird252]

Hi ACP - It is an important phase of flight when you change from flight level to altitude
(1013 to QNH) whether climbing or ascending. You can instruct a Flight Management Computer (FMC) to do most things, but changing the Altimeter setting is a big part of the relevant manual checks while leaving or approaching an airport. Important for traffic seperation while climbing, and important for height above ground information while decending.

Hope this helps - if not, shout and ill have another go!!

[HugMonster]

ACP, you could also write to the Safety Data Department at the CAA, Aviation House, Gatwick, RH6 0YR. They'll be able to give you a load of info on individual level busts.

A common cause of level busts is that SID's (Standard Instrument Departures) in the UK, with the exception of Birmingham, finish at an altitude (based on QNH, ambient atmospheric pressure). Onward clearances are usually to a flight level (based on standard altimeter pressure setting 1013 mb). If a crew forget to change altimeter settings when they receive their onward clearance, and the mistake is not subsequently detected, they may end up levelling off at, say, 15,000' amsl (on the QNH). If QNH is less than 1013 this will result in their having levelled off higher than FL150. If the pressure difference is more than (approximately) 7 mb, the altitude difference will be greater than 200', resulting in a level bust.

For this reason ATC will shortly start issuing onward clearance which, when clearing from an altitude through Transition Altitude to a Flight Level, using the following phraseology:-

"XYZ123, climb Flight Level 150, set altimeters standard 1013."

Hope this is all clear enough!

[eyeinthesky]

Nobody has yet mentioned perhaps the biggest cause of level busts: human error. This is when the flight crew set the wrong level in the altitude window, or when ATC want you to climb/descend to level X but actually say level Y and miss the readback.

Phraseology can also play a part. in the Good Ol' USofA "Maintain" also means climd/descend. There have been a few incidents where traffic at (for example) FL390 has been told to maintain FL 350 (ATC slip of the tongue) and rather than querying the difference, down it went, right through the FL370 sitting just behind it!.. But then the Americans have always been a bit different!..



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"Take-off is optional, Landing is mandatory"

[411A]

Eyeinthesky
Clearly the Brits have a problem in the USA. BA in PHX two weeks ago was told to descend to 6000ft, but leveled at 7000 instead. I guess that the "recent" changes to the UK procedures...."set altimeters standard 1013" is needed as they don't seem to listen, let alone understand.

[HugMonster]

As far as I am aware, use of the word "Maintain" in ATC instructions is not ICAO. Because of the possible confusion mentioned by eyeinthesky, ATC in the UK is being told not to use it at all.

411A, yes, often Brits do have a problem in the USA. It's not only over-simplistic but also insulting to say that "they don't seem to listen, let alone understand". What's more, comments like that do not aid the situation, nor assist in understanding a potentially very dangerous problem. US pilots often have difficulty in the UK in exactly the same way. Part of the problem is difference of accents, part is that US Aviation English has numerous (unfiled) differences from ICAO standard, part is that US ATC and pilots don't even stick to their own "standards".