View Full Version : Take Off Criteria for Boeing NG A/C?
I was told that on Boeing NG A/C, there was a trade off during certification of Take Off Performance:
For a lower screen height - 10' instead of 35' - Boeing NG A/C must use WET Take Off numbers when the runway is wet - rather than those numbers being "advisory." Skid resist plays a part here also - but for now I'd like to limit this discussion to just having wet or dry available.
Don't have the official AFM with me now and it won't give the reasons anyway.
BTW - got lot's of opinions on this - it was discussed in a bar - would like responses with references if possible.
Thanks for any factual information that can be provided,
LL
What makes this different to any other airliner? We do the same on all of them!
The reason why the "WET" data is no longer "advisory" is because the FAA finally incorporated the requirement for this data into the FARS.
Mutt.
Are you saying that all airliners no longer have asvisory wet data or only those certified after a date? - wis that FAR 121 or 25?
"What makes this different to any other airliner? We do the same on all of them!
The reason why the "WET" data is no longer "advisory" is because the FAA finally incorporated the requirement for this data into the FARS."
have another coffee
21st Oct 2002, 11:00
Caused by the UK CAA and also believe JAR's. These require new aircraft to be certified with wet runway performance figures. As that is/was not required in the USA it would cost huge amounts of money and performance penelties if it was not properly done. So somehow they agreed on a simplyfied performance reduction by adding a weight penalty AND reducing screen height in order not to suffer to much on take-off perfomrance.
There was a year ago also a discussion about, but can't find it
Sec. 25.109 Accelerate-stop distance.
Federal Register Notes
63 FR 8298, No. 32, Feb. 18, 1998
SUMMARY: This action amends the airworthiness standards for transport
category airplanes to: revise the method for taking into account the time
needed for the pilot to accomplish the procedures for a rejected takeoff;
require that takeoff performance be determined for wet runways; and require
that rejected takeoff and landing stopping distances be based on worn brakes.
The FAA is taking this action to improve the airworthiness standards, reduce
the impact of the standards on the competitiveness of new versus derivative
airplanes without adversely affecting safety, and harmonize with revised
standards of the European Joint Aviation Requirements-25 (JAR-25). These
standards, which affect manufacturers and operators of transport category
airplanes, are not being applied retroactively to either airplanes currently
in use or airplanes of existing approved designs that will be manufactured in
the future.
EFFECTIVE DATE: March 20, 1998.
Give them another 10 years and they might wake up to the reality of contaminated runway operations!
Mutt.
Mutt:
Thanks for the informative reply - just so I can take this stuff back to the bar and explain it to them - regarding the phrase:
"reduce the impact of the standards on the competitiveness of new versus derivative airplanes" - & - "These standards, which affect manufacturers and operators of transport category
airplanes, are not being applied retroactively to either airplanes currently in use or airplanes of existing approved designs that will be manufactured in the future. "
These statements wouldn't infer that these criteria don't apply to the B-737-700 because it is "airplanes of existing approved designs" - namely a B-737 - which was "manufactured in the future" as a B-737-700 - would they?
Trouble is - there's a lot (at least at the bar) who seem to believe that is true - and statements in the AFM are not exactly concrete in stating that WET runway criteria MUST be used, if the runway is not dry, on any A/C built after 1998 even though it was a derivative.
So - to us laymen down at the bar (Pub would probably better so as not to confuse it with the legal bar) - is there any more definitive statement that makes is clear - without the Yada, Yada, Yada about derivites & future manufacture A/C from a existing design.
Thanks again for your informative reply and any future posting which would clarify it for the Pub Crawlers.
LL
Trouble is - there's a lot (at least at the bar) who seem to believe that is true - and statements in the AFM are not exactly concrete in stating that WET runway criteria MUST be used, if the runway is not dry, on any A/C built after 1998 even though it was a derivative.
Loke, i dont have a -700 AFM yet... I only have the FPPM and some software programs, but the wording in the FPPM when compared to the 744 or 772 is completely different in that it talks about the WET surface with the reduced screen height!
As for the pure definition of "derivative", I dont have it, but you surely cant compare the NG aircraft to the -100~~!
Interesting enough on my FAA licence i can fly ALL models of the 737...... I wonder if the JAA would accept that idea!
Mutt.
PS, does that bar sell GOOD Guinness?