Takeoff Thrust Time Limit 5/10 minutes

[AeroTech]

Hi,

Takeoff thrust may be used only for a maximum of five minutes, with one exception: the time limit is extended to ten minutes for airlines that have purchased a special Airplane Flight Manual appendix called the “ten-minute appendix”. The Certificate Limitations section of that appendix states specifically:
“The time limit on the use of takeoff thrust is increased to 10 minutes provided this use is limited to situations where an engine failure actually occurs and there is an obstacle in the takeoff flight path.”

I thought the takeoff thrust time limit is 5 minutes with AEO and this time is increased to 10 minutes regardless of the existence of an obstacle in the takeoff path. What do you think?
Is the 10 minutes time limit a basic item in all airliners or an option that an airline/operator has to purchase?

Assume there is engine failure during takeoff after V1. For some reason the crew during the turn back want to perform a go-around. The 10 minutes takeoff thrust time limit may be already exhausted before the Go-around.
I am wondering if the crew can use takeoff thrust during the go-around or the crew must land ASAP without go-around.

Feedback appreciated.
Regards

[wileydog3]

Never confuse 'Normal" procedures with non-normal (emergency)events. In the case of an engine failure you do what is necessary. If you only need normal thrust to remain airborne, fine. On the other hand, if 'radar thrust' is required (where you shove the thrust levers through the radar), use radar thrust. This is, of course, for jet engines. Recips tend to be much fussier and more demanding.

But the focus shifts from normal temps, limits, time to getting the airplane safely back on the ground. More often than not, normal limits will not be exceeded but the mindset has to be changed to using whatever is required to be successful.

[galaxy flyer]

AeroTech

Where did that quote come from? In most FAR 33 engines, I think the allowance is 5 for AEO and 10 for OEI. But, remember, that is not total time, but continuous time, so if you used the 8 of the 10 in your OEI climb and acceleration and pull the power back to CLB after clean-up, you know have another 10 minutes of TO power should you need in on the go.

And as Wiley says, in any emergency, use what is required, engines are pretty tough.

GF

[sevenstrokeroll]

I remember that the JT8D could handle FIREWALL POWER/RADAR POWER for 8 minutes before it started to become damaged.

and'that's more than takeoff thrust

[ImbracableCrunk]

One of my 737 manuals says for the Classic it's 5 mins for T/O, and for the NG it says 5 mins or 10 mins OEI.

My other company's 737 says 5 mins, but for a few hulls it's 10 mins (no mention of OEI).

That leads me to believe that, on the 737 at least, that there are options.

I'm guessing that this is really for the bean counters, and not for the pilots. Who wouldn't set radar power if we're going down, Larry?

[HazelNuts39]

Is the 10 minutes time limit a basic item in all airliners or an option that an airline/operator has to purchase? It is not a basic item for all airliners but needs to be specifically approved during certification of both the engine and its installation in a particular airplane. I believe approval for engine certification is a formality, but the certification for the airplane requires demonstration of adequate cooling of the engine bay for the longer time. To take advantage of the extended time limit in the scheduling of obstacle-limited take-off weights, you may need additional OEI take-off flight path data for far-away obstacles.

regards,
HN39

[BOAC]

wiley - this has NOTHING to do with firewalling the throttles - the 5/10 determines the ability for terrain avoidance up to 'clean' which may limit the RTOW tables for a given runway and/or require an EOSID. It is for planning purposes only. If you need more in an emergency, you use it!

[Avenger]

Absolutely agree with BOAC, Terrain clearance and the need to have an EFP or EOSID is one way of looking at it. Caveat, use all the power available if needed!

[AeroTech]

Hi,

I get this quote from Boeing document "Jet Transport Performance Methods": an online document (I guess it's not an official document).

Here a quote from "Getting to Grips with Aircraft Performance" (Airbus document, I guess also it's not an offcial document)
"The TakeOff (TOGA) thrust represents the maximum thrust available for takeoff. It is certified for a maximum time of 10 minutes, in case of engine failure at takeoff, or 5 minutes with all engines operative"

In Airbus document they didn't mention the obstacle in the takeoff path.

Regards

[FE Hoppy]

10 minute option is available on the CF34-8s and 10s on the Embraer Jets. A couple of operators have the option due to their hot/high ops and the need for extra take of performance.

As had been said, it's for the certified performance. If you needed it for longer in reality you would use it. The engine won't explode at 1 second past the limit!

I would have to go to the source docs to confirm but I seem to remember the time limit being quoted as 10 minutes for the take off and a further ten minutes for a go around in the certification demonstration. That doesn't tie in with the poster who claimed you could just back it off for a bit then fill your boots with another 10 minutes worth.

[galaxy flyer]

FE Hoppy

That is what I stated, 10 minutes (if that is what is certified) in the event of a engine loss on takeoff; then 10 minutes "on the go" OEI. During maneuvering and approach the engine should be (and will be considered to be, be the authority) at MCT or less.

GF

[Avenger]

10 minutes at full T/O thrust is considered to be one continuous period, and as then long as you want at MCT, that's why it's MCT. You cannot take off and reduce the thrust, then set MCT, then start again the timing for T/O thrust and keep nibbling away at the 10 minutes allowance..

[barit1]

OTOH -

If you NEED more than 5 (or 10) minutes, DON'T think you are doing the donk a favor by retarding to MCT to reset the clock, then re-advancing to TOGA. The hardware would prefer that you maintain a constant thrust setting for as long as required, and not down then back up.

Just sayin'.