Help with the Boeing 787 ETOPS calculations

[Arzenim]

Hi guys,
Could someone please tell me what average calculated distance do airlines use for the B788 and B789 for one hour worth of flying time when calculating ETOPs ?

Thanks and best regards

[broompusher]

Between the 2 different companies I've flown 787s for, one used 426NM and the other used 441NM. IF you're flying a 787 with the RR Trent engines, the ETOPS limitation is 352NM for the time being.

[Arzenim]

Thanks alot @broompusher

[Sidestick_n_Rudder]

Mine uses 447 Nm. Operator may choose any speed that suits them up to Vmo

[Cough]

Originally Posted by broompusher

IF you're flying a 787 with the RR Trent engines, the ETOPS limitation is 352NM for the time being.

May I ask how is that figure derived?

[Dave Therhino]

There is a single engine diversion speed restriction on the airplane applied by Airworthiness Directive 2018-08-03 to avoid single engine operation of the remaining engine in a condition that can cause compressor blade resonance and resultant engine failure. The same AD limited certain RR powered 787s to a 140 minute diversion time. The AD applied those restrictions via AFM limitations.

http://rgl.faa.gov/Regulatory_and_Gu...2018-08-03.pdf

[Smythe]

2019.
The new mandate, issued by FAA with a Feb. 4 effective date and expected to be adopted globally, limits extended range (ETOPS) operations for "Package B" Trent 1000s with more than 1,000 cycles on its intermediate pressure compressor (IPC) blades to 180 min. from the nearest suitable airport.

The fatigue-cracking issue was discovered on newer-standard Package C-configured engines, leading to inspection mandates and a 140-min. ETOPS limitation

https://www.mro-network.com/engines-...s-powered-787s

What is with all of the blade issues?

[Dave Therhino]

All correct. I mentioned only the earlier AD for the package C engines because that was what drives the reduced ETOPS circle radius per unit of time (due to AFM speed limitation) that "Cough" asked about. AD 2019-01-01 made no changes to AD 2018-08-03.

[Cough]

Dave,

Fully familiar of the difference between the ETOPS 140/180 minute rules. My question is how that affects the 1 hour ETOPS distance... Say we call the ETOPS distance 400nm the max ETOPS diversion distance is 3x400=1200nm for 180min or 14/6*400=933nm for the 140min rule. In my mind though, that doesn't affect the 1 hour ETOPS distance which would stay at 400nm.

Also... I've flown many 787's with Trent TEN and pack B engines with no limitation below 180min, and also many pack C engines (obviously with less than 300 cycles on them) which were also 180min so where broompusher stated the limitation for all Trent 1000's on a 787 is 352nm it raised my curiosity level.

[Dave Therhino]

The difference is caused by the speed restriction that is included in the AFM limitation required by AD 2018-08-03 for airplanes with Package C engines. In addition to the 140 minute limit, the limitation also states, "ETOPS single engine driftdown diversion must be planned and flown at engine-out long range cruise speed." This speed is less than the speed operators normally use for ETOPS route planning, so the ETOPS circle radius per hour of diversion flight is less than it would be if there was no speed restriction. The speed restriction results in engine operating conditions that reduce the chance of sitting on a blade resonance. The later AD for package B engines did not have this speed restriction.

[Cough]

Using the QRH EO LRC values for mach at mid weights (very high weights of course not permitted under the 140min) I'm getting a TAS of around 390-400kt... I get close to his figure if I take his diversion distance and factor it by 14/18'ths. So I don't know whether the operator has chosen to use a reduced speed figure to draw 3 hour circles which are compliant with the 140min figure. Hence my question...

[Sailvi767]

You are not required nor is it desirable to use single engine long range cruise in a engine out ETOPS situation. In most ETOPS diverts the issue is going to be high gross weight landing due to having to much fuel onboard.

[Cough]

Originally Posted by Sailvi767

You are not required nor is it desirable to use single engine long range cruise in a engine out ETOPS situation. In most ETOPS diverts the issue is going to be high gross weight landing due to having to much fuel onboard.

Except the exceptional case relating to the Airworthiness Directive for the 787, with RR Trent 1000 pack C engines, with either engine >300 cycles requires it. See the FAA AD can be seen here. The requirement is stated on page 7