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FAR Amendment 25-92  
User currently offlinesmartt1982 From United Kingdom, joined Nov 2007, 225 posts, RR: 0
Posted (2 years 6 months 2 weeks 5 days 8 hours ago) and read 2992 times:

Recently was trying to get my head around certification procedures and came across this.

“Amendment 25-92 of the FARs required inclusion of wet runway takeoff performance in the AFM”

Why was this not part of the certification before?, what happened or changed that caused this to be brought in? I take it that “advisory” information on Wet runways was available prior to this. Will this be the same for contaminated runways, as in at the moment all that needs to be provided is advisory information but later on actually certified info will need to be produced?

Airplanes Not FAA Certified for Wet Runway Takeoff Accountability

How was it that aircraft that were certified prior to this amendment then go on to get certified info for Wet Runways in their AFMs?

Why is there no clearway credit allowed for wet runway since this ammendant?

http://www.scribd.com/doc/36139142/T...-Contaminated-and-Slippery-Runways

[Edited 2012-06-10 15:35:02]

5 replies: All unread, jump to last
 
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 1, posted (2 years 6 months 2 weeks 5 days 8 hours ago) and read 2977 times:

Quoting smartt1982 (Thread starter):
Why was this not part of the certification before?

It was. This amendment requires that it be in the AFM. The data always existed.

Quoting smartt1982 (Thread starter):
what happened or changed that caused this to be brought in?

A bunch of runway overruns.

Quoting smartt1982 (Thread starter):
I take it that “advisory” information on Wet runways was available prior to this

Yes.

Quoting smartt1982 (Thread starter):
Will this be the same for contaminated runways, as in at the moment all that needs to be provided is advisory information but later on actually certified info will need to be produced?

Unknown...I haven't seen an NPRM proposing the same change for contaminated runways but it would be consistent.

Quoting smartt1982 (Thread starter):
How was it that aircraft that were certified prior to this amendment then go on to get certified info for Wet Runways in their AFMs?

The data exists, the OEM's collected it during the performance phase of flight testing. They just didn't put it in the AFM because there was not requirement to do so; for a bunch of reasons, you try to keep the AFM as minimal as you can.

Quoting smartt1982 (Thread starter):
Why is there no clearway credit allowed for wet runway since this ammendant?

They generally don't allow doubling things up to make sure the calculations are conservative. The precedent exists for other types of takeoff/landing configurations already.

Tom.


User currently offlinesmartt1982 From United Kingdom, joined Nov 2007, 225 posts, RR: 0
Reply 2, posted (2 years 6 months 2 weeks 5 days 8 hours ago) and read 2962 times:

Thanks Tom

That is so much more clearer.

What is the reason they have data from tests on for example the 747-100 for the CAA, did the CAA require more stringent data than was needed for the FAA?, is this again the case that Boeing had all the data (such as from the CAA) but did not have to use it for the FAA AFM?

Quoting tdscanuck (Reply 1):
They generally don't allow doubling things up to make sure the calculations are conservative. The precedent exists for other types of takeoff/landing configurations already.


"Current certification standards and implementation of digital performance information allow the inclusion of clearway credit on wet runways for the engine-out case for both the 747-400 (100%) and the 777-200/300 (50%). Depending on the particular conditions this may result in the scheduling of lift-off very near the end of the runway threshold in case of an engine failure."

Came across this, I was wondering but isint this what would normally happen? In the case of an engine failure, the aircraft will be reaching its 35ft above the end of the runway/threshold? Is it because the clearway credit has been used and because its wet the screen height will only be 15ft, but surely if the aircraft is only getting airborne at the end of the run the clearway is an added protection?


Any tips/info on how to increase/get a more in-depth detailed knowledge of Aircraft certification (Both FAA and EASA) and performance?, i.e. books/courses etc.
Cheers
Steve

[Edited 2012-06-10 16:34:59]

[Edited 2012-06-10 17:20:38]

[Edited 2012-06-10 17:21:51]

User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 3, posted (2 years 6 months 2 weeks 5 days 5 hours ago) and read 2926 times:

Quoting smartt1982 (Reply 2):
What is the reason they have data from tests on for example the 747-100 for the CAA, did the CAA require more stringent data than was needed for the FAA?

I'm not sure in that particular case, but it's not at all unusual for different regulators to have slightly different requirements. The OEM will get all the data, then present each regulator with that subset of data that they require.

Quoting smartt1982 (Reply 2):
is this again the case that Boeing had all the data (such as from the CAA) but did not have to use it for the FAA AFM?

That appears to be the case, yes.

Quoting smartt1982 (Reply 2):
Came across this, I was wondering but isint this what would normally happen? In the case of an engine failure, the aircraft will be reaching its 35ft above the end of the runway/threshold? Is it because the clearway credit has been used and because its wet the screen height will only be 15ft, but surely if the aircraft is only getting airborne at the end of the run the clearway is an added protection?

The clearway credit pushes the obstacle clearance height out so that you only have to be airborne by the end of the runway, rather than actually over a particular screen height. So, an takeoff that's one-engine-go limited and was done with a clearway could result in rotation very near the end of the pavement. It wouldn't take much to turn it into an overrun.

Quoting smartt1982 (Reply 2):
Any tips/info on how to increase/get a more in-depth detailed knowledge of Aircraft certification (Both FAA and EASA) and performance?, i.e. books/courses etc.

Boeing Flight Training does an excellent takeoff/landing performance course (http://www.boeing.com/commercial/aviationservices/flight-services/flight-operations/performance-engineer-training.html) . I assume Airbus has something similar. That covers, in a lot of depth, how the performance is calculated.

On the certification side, the Holy Bible of certification for FAA flight testing is Advisory Circular (AC) 25-7B:
http://www.faa.gov/documentLibrary/media/Advisory_Circular/25-7B.pdf

Performance starts on p.17.

Tom.


User currently offlinesmartt1982 From United Kingdom, joined Nov 2007, 225 posts, RR: 0
Reply 4, posted (2 years 6 months 2 weeks 4 days 20 hours ago) and read 2844 times:

Quoting tdscanuck (Reply 1):
A bunch of runway overruns.

With regards to this, for our airline operation in Europe (So hence CS25 and EU OPS) for our dispatch requirments we have the following

Dry Rwy LDR = Actual Dry Rwy LD x 1.67

Wet Rwy LDR = Dry LDR x 1.15

These are obviously the CERTIFIED Distances from Boeing and are from the AFM

We are also required to check for Dispatch the Contaminated/Slippery LD which is the higher of 1 and 2

1. Dispatch Contaminated/Slippery LD (Am I right in thinking that this one is advisory but our regulators want it checked prior to dispatch, what is confusign here is that it states this one has no reverse thrust credit which could make it look it was a certified distance or are they just being conservative?)
2. Dispatch Wet Rwy LD

In regards to the FAA prior to this admendment, were flight crews required prior to dispatch to check landing distances for expected weights for Wet or even contaminated/slippery from the Advisory info(as instructed in Part 121 perhaps) even though it was not certified.

Does changing the info from advisory to certified as was the case with 25-92 just make it more stringent as in the airlines were focred to follow it more closely perhaps? I take it prior to this airlines would still check Wet Landing distances prior to dispatch?

Again in regards to the certified landning distance ie Boeings Demo flight test as well as other OEM, what is the reason behind not using thrust reversers for the test?

Where do Boeing carry out these tests and is there any photos/videos? all I have seen is the odd high speed RTO test of the 747.


User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 5, posted (2 years 6 months 2 weeks 4 days 18 hours ago) and read 2825 times:

Quoting smartt1982 (Reply 4):
In regards to the FAA prior to this admendment, were flight crews required prior to dispatch to check landing distances for expected weights for Wet or even contaminated/slippery from the Advisory info(as instructed in Part 121 perhaps) even though it was not certified.

It all depends on the OpsSpecs, but I believe the answer is "yes" for most airlines.

Quoting smartt1982 (Reply 4):
Does changing the info from advisory to certified as was the case with 25-92 just make it more stringent as in the airlines were focred to follow it more closely perhaps?

They don't even have to follow it then (they have to follow the OpsSpec, which can deviate), but it gives the data more "weight."

Quoting smartt1982 (Reply 4):
I take it prior to this airlines would still check Wet Landing distances prior to dispatch?

I would certainly hope so.

Quoting smartt1982 (Reply 4):
Again in regards to the certified landning distance ie Boeings Demo flight test as well as other OEM, what is the reason behind not using thrust reversers for the test?

Part is conservatism, part is allowing thrust reversers to be on MEL without having to adjust all the landing data, part is taking account for the fact that thrust reversers rarely announce a fault until you try to deploy them (at which point it's too late), and part is that it doesn't make any difference to most landings because most landings are done on autobrake and thrust reverse makes no difference to stopping distance when you use autobrakes.

Quoting smartt1982 (Reply 4):
Where do Boeing carry out these tests and is there any photos/videos? all I have seen is the odd high speed RTO test of the 747.

Absent an overriding constraint (particular weather, particular runway slope, etc.) most of it is done at Edwards Air Force Base in California, Victorville Logistics Airport in California, and Moses Lake ("Grant County International") in Washington. The common thread there is good weather, low traffic, and a *huge* runway. Moses Lake also has the added benefit of being about 20 minutes from Seattle.

Unusual requirements can drive some one-offs...autoland with an abrupt step is done over the seawall at SFO, upslope/downslope is out of a couple of places in Wyoming, winds are done wherever you can get the conditions (often Keflavik Iceland but only if you have to), screwing with the lights or ILS beam is usually done at Glasgow Industrial Airport in Glasgow Montana (Boeing owns the entire airport), water ingestion is done at Roswell, New Mexico, high altitude is done at Colorado Springs or La Paz, Bolivia, etc.

Tom.


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