PDA

View Full Version : 737NG tail wind limit


citizensun
1st Sep 2010, 13:30
hi all~
according to the flight manual ,the auto landing wind limit are, head wind 25kts;cross wind 20kts; tail wind 15kts; and there a explaination underneath: when the tail wind exceeds 10kts, there maybe some operation restriction.
and still in that book, says the tail wind operation limit for the take off and landing is 10kts:sad::sad::sad:
someone shed some light?
what kind of restriction if the tail wind exceed 10kts during autolanding?

PLovett
1st Sep 2010, 13:45
Desperation?

citizensun
1st Sep 2010, 13:48
:ugh::ugh::ugh:

Callsign Kilo
1st Sep 2010, 13:50
I think desperation is pretty apt because a dual channel tailwind landing in the NG isn't a pretty affair. I wouldn't want to test 15kts in anger, certified or not.

You are always restricted by the PI index. Boeing recommends a further 140m for F40 when dual channel. We have max landing weight charts for some destinations in relation to dual channel approaches. Any degree of tailwind restricts the hell out of the aircraft. If it were me I'd be looking elsewhere...

Equally we have some destinations that allow for 15kts tailwind landings. Otherwise company policy is 10kts. For takeoff max 10kts. Yet always respect the PI for landing or performance manual at the planning stage. Equally the RTOW for departure. Fairly simple set of rules.

BOAC
1st Sep 2010, 13:55
cs - the limits I am used to are 25/15/10kts. I understand 15kts is 'available' from Boeing if your company pays for the figures. What do you mean by the 'Flight Manual'? Is that a Boeing or a company document?

fireflybob
1st Sep 2010, 13:58
The 10 kt limit is a performance limit, I think, because the data only goes up to 10kt tail. If you want data for 15 kt tail then I believe you'd have to ask Boeing and there would be an extra charge, I guess.

Historically I think it was Britannia Airways who were the first to put the B737-200 on the UK register in the 1960s. They asked Boeing to provide data for 15 kts tailwind - a wise move since in those days not many airports had ILS on both ends and also the policy was better to take off with a tailwind in a direction that avoided an emergency turn in the event of engine failure.

As has been said before whether you want to autoland with 15 kts tail is another matter. Also airports sometimes apply restrictions. If you look at the Notams for Nantes (LFRS) there is a note about autoland with "rear wind" - sounds a bit painful to me......

Callsign Kilo
1st Sep 2010, 14:00
citizensun may have a fail operational autopilot systems? Limitations I believe are higher?

citizensun
1st Sep 2010, 14:11
it`s a company customized boeing flight manual. it`s 737-800
i can`t find any clue wether my company pay for that extra 5 kts "rear wind":}:} or not .
it only says when forecasted weather condition is at the minima( i don`t what this mean, CAT 1 or something else), the autoland tail wind limit is 15kts, and there is a note : there maybe some retriction on operation.
it looks A Pump`s company have the similar policy with mine.
can you tell me something about what you said " Cat 1 we could have 15kts tailwind on certain aerodromes. "? please~~:ok:

Denti
1st Sep 2010, 14:56
Autoland limits for fail operational are 25 headwind, 25 cross, 20 cross OEI, 10 tail. We do have nearly all our planes certified for 15 kts tailwind take off performance, but none for 15 kts landing performance. Fail operational landing performance is really great compared to fail passive one, there is a distinct increase in margins compared to the old ones.

PEI_3721
1st Sep 2010, 16:13
I posted this in the AA Jamaica thread;-
Re tailwinds: The Flight Test Guide for Certification for Transport Category Airplanes AC 25-7A states “The AFM should contain a statement that the limitation for tailwinds greater than 10 knots reflects the capability of the airplane as evaluated in terms of airworthiness but does not constitute approval for operation in tailwinds exceeding 10 knots".
AFAIK, the 737 AFM has no such statement, thus this suggests that if ‘operational approval’ it has been given by the local FAA. In this processes there is opportunity for an ill-considered approval (e.g. use the same one as previous 737 variants), and perhaps without full consideration of the potential risks which perhaps the certification regulations suggest.

IMHO extending a tailwind landing limit adds considerable risk to an operation and should be avoided. There are many performance variables which can be affected (e.g. tyre speed limit) and the margins for the assumed crew performance e.g. tendency for a long landing, are greatly reduced.

The bottom line for an approval might be if the approved flight manual contains the landing data or not – do not assume that the computerised landing data or system limits are evidence of an approval to operate.


“… what kind of restriction if the tail wind exceed 10kts during autolanding?”
Perhaps landing performance.
Autolanding uses a different test method from manual landing to establish the landing distance. e.g. (not factual) 1000 ft air distance for manual landing, 2500 ft for autoland.
Or operational approval.
An aircraft may be certificated for an operation, but the operator is not (training, experience etc).

citizensun
1st Sep 2010, 16:46
i checked the wiki and find that:
"Fail-passive autopilot: in case of failure, the aircraft stays in a controllable position and the pilot can take control of it to go around or finish landing. It is usually a dual-channel system.
Fail-operational autopilot: in case of a failure below alert height, the approach, flare and landing can still be completed automatically. It is usually a triple-channel system or dual-dual system."
737-800 autoland is a dual channel system, so it doesn`t look like a fail-operational autopilot.
maybe as PEI said , limitation for tailwinds greater than 10 knots reflects the capability of the airplane as evaluated in terms of airworthiness but does not constitute approval for operation in tailwinds exceeding 10 knots".
thank you all, i kind of sort this thing out~
but i still need to verify with my company~
:ok::ok::ok:great appreciation!

Denti
1st Sep 2010, 19:06
Fail operational doesn't have to be triple channel, in fact it is only dual channel for quite a few aircraft including the A320 series. And it is only an option for the 737 that many operators do not choose as it costs quite a bit more and means more maintenance, however it provides much better autoland performance, autoland with OEI and slightly better crosswind limits, oh, and of course automatic rollout.

Cough
1st Sep 2010, 19:28
320 is a bit different, as each channel has an autopilot and monitor. Hence you can cat3a auto land with only one autopilot engaged. 737 depending on model ordered is different in that regard.

PEI_3721
1st Sep 2010, 19:30
Beware Wiki information, it is not regulatory approved.
Autopilot definitions in EU – AWO. (www.easa.eu.int/ws_prod/g/doc/Agency_Mesures/Certification_Spec/decision_ED_2003_06_RM.pdf)
FAA requirements are similar if not identical.

john_tullamarine
2nd Sep 2010, 01:14
10 kt tail has been the routine certification limit for aeons. AFM approval to go beyond it is an over and above exercise for which, as others have observed above, you can expect to pay handsomely.

Be aware that there be dragons associated with excess tailwind operations and those TPs who have been tasked with such testing usually have a few hair-raising tales to relate over an ale.

bigduke6
2nd Sep 2010, 07:37
To answer the original question of:

"what kind of restriction if the tail wind exceed 10kts during autolanding?

The restrictions are likely runway condition (dry, not wet) and a total wind or gust limitation. You could have a 15 kts tailwind component approved, but only if TOTAL report wind is less than XX kts, or gusts 5 kts or less, etc. This is to try and avoid you actually having more than the 15 kts that you calculated at the time of landing.

Only place where I know it is routinely used is in Japan, to avoid circling.

john_tullamarine
2nd Sep 2010, 07:51
Only place where I know it is routinely used is in Japan, to avoid circling.

Plenty of folks have the certification and operational OK for 15kt and I have seen the odd AFM up to 20 kt.

However, there are potential handling problems so it is not appropriate for an ad hoc "let's go anyway" approach

NorthSouth
2nd Sep 2010, 08:58
I'm very much an outsider to this discussion but I'm interested that it only refers to autoland. Are there different tailwind limits if it's a manual landing, and is the approval mechanism different if you want approval to land in >10kts manually?
NS