Federal Aviation Administration

Summary of Meeting with Rolls-Royce plc for Regulatory Docket No. FAA-2013-1049

Date of Meeting: March 13, 2014

Attendees:

Federal Aviation Administration

Vincent Bennett, Esq., ANE-7, (781) 238-7044

Thomas Boudreau, ANE-140, (781) 238-7140

Anthony Cerra, ANE-142, (781) 238-7128

Diane Cook, ANE-111, (781) 238-7111

Tara Fitzgerald, ANE-111, (781) 238-7130

Robert Ganley, ANE-110, (781) 238-7110

Karen M. Grant, ANE-142, (781) 238-7142

Robert Green, ANE-142, (781) 238-7754

Alan Strom, ANE-111, (781) 238-7143

Thomas Thorson, ANM-140S, (425) 917-6508 

Rolls-Royce plc

Dave Brown, (44) 1332 24 6640

Richard Corran, (44) 7794 21 4351

Neil Davies, (44) 1332 82 3304

Colin French, (44) 1332 70 8343

Gareth Jones, (44) 7794 21 4217

Iain Park, (44) 1332 24 9292

Paul Stow, (44) 1332 82 3516

Belinda Swain, (44) 7837 37 6396

I. Purpose of meeting

Purpose of the meeting is for Rolls-Royce to present to the FAA whatever information 

Rolls-Royce deems necessary to fully respond to FAA questions.

II. Outcomes

 Rolls-Royce to have communicated all the information needed to clarify their 

answers to FAA questions.

 Rolls-Royce will have submitted all the information for FAA to determine the 

outcome of the petition for exemption.
III.Rolls-Royce addressed the following FAA clarifying questions:

1. Please clarify your response for why the exemption is needed by providing data to 

show why the Trent 1000 Package C configuration does not meet 33.27 

requirements while previous Trent 1000 models met the requirement. 

o Rolls-Royce provided an overview of the exemption request.

o Rolls-Royce provided description of historical experience of the HP 

shaft system within the three shaft engine design.

2. Please clarify what testing Rolls-Royce has done on Trent 1000 Package C 

configuration engines to support your terminal speed estimates. 

o Rolls-Royce provided a description of the derivation of HPT terminal 

speed and determination of HPT disc capability.

 Engine conditions at all potential terminal speed conditions 

identified.

 Thermodynamic assessment of the turbine behaviour post 

shaft failure.

 Worst-case turbine inertia used in the assessment.

 Performance data validated by real engine experience.

 Frictional effects are based on real engine experience.

 Capacity and efficiency understanding validated by engine and 

rig test.

 Control system behaviour understood.

 Terminal speed calculation methodology is validated.

 HPT disc capability proven by test at temperature.

3. Please clarify your response to which models require the exemption by providing 

the terminal speeds and margins for each model.

o Rolls-Royce provided engine overspeed margin comparison for each 

model.

4. In the Compensating factors for exemption from Section 33.27(f)(6) report, 

DNS192492 iss1, Rolls-Royce notes that no failure of the HP shaft system torque 

path on the Trent family of Rolls-Royce large, civil, 3-shaft turbofan engines in 

more than 228 million flight hours service experience supports a probability of 

failure rate of 3.1x10-9 failure per flight hour. The cited experience dates back to 

1972, encompasses all 3-shaft service experience, but only through October 2012. 

What is the sum of the service experience and associated failure rate through the 

end of December 2013?

o Rolls-Royce provided detailed summary of fleet hours and flight 

cycles for RB211-22B, RB211-524B, B3 and B4, RB211-524B2 and C2, 

RB211-524D4, RB211-524H and H-T, RB211-524G, H, G-T and H-T, 

RB211-535C, RB211-535E4 and E4-B, Trent 700, Trent 800, Trent 

500, Trent 900, and Trent 1000 engines through December 2013.
5. Please clarify how the cited service experience (i.e., 244 million hours without a 

failure) is relevant to the Package C1 and associated derivative engine models by

providing:

a. A summary of the HPT maximum permissible (redline) speeds, disk burst 

speeds, and predicted HPT rotor terminal speeds for a shaft system 

separation, with a description of the prediction method used for the 

terminal speed calculation for the RB211 and Trent family of engines; and

b. Detailed descriptions of any rig, engine tests, or other experience used for 

validation of the analytical model used to predict terminal rotor speeds due 

to the HPT rotor loss of load for the Package C1 engines.

Ref Question a., 'the 2nd question' as answered by Iain Park 3/6/14 at 12:59 PM.

Please provide the burst speeds and predicted terminal speeds for the HPT of the 

historical service engines.

o Rolls-Royce provided an engine overspeed margin comparison for 

the Trent 1000, Trent 500, Trent 800, Trent 900, RB211-524, and 

RB211-535 engines for terminal speed and redline conditions.

o Rolls-Royce provided detailed descriptions of the engine testing 

used to derive HPT terminal speed.

 The modelling method has been validated against IP 

turbine shaft failure events. HP shaft failure has not been

directly validated as RR has never had an HP Shaft failure.

6. Rolls-Royce stated that the cited service experience supports a probability of 

failure rate of 2.87x10-9 failures per flight hour. Please clarify the HPT shaft 

experience on RB211 and Trent engines that apply to the Trent 1000 Package C1 

engines by providing stress levels, normalized bulk stress and peak featurespecific stress values, and calculated lives for both the Package C1 HPT shaft 

system, and for the HPT shafts on the other engine models used to show how the 

reliability calculation is 2.87x10-9 failure per flight hour is applicable to the 

Package C1 models.

Ref Question a., 'the 2nd question' as answered by Iain Park 3/6/14 at 12:59 PM.

Rolls-Royce provided ratios of stress to ultimate stress to show the Package C 

design is in the family of historical service engines. Ref. EDMS01000175101 Iss 

2 (12/8/13).

Please provide the associated actual stress levels and ultimate stress figures that 

were used for each ratio number provided in the report.

Ref Question a., 'the 2nd question' as answered by Iain Park 3/6/14 at 12:59 PM.

Please provide the part life values in the drive arm areas of the HPC and HPT, and 

any mini-disc lives, for the Package C design and the historical service engines.

o Rolls-Royce provided safe lives and stress levels in the HP shaft 

section for Trent 1000 Package C1, Trent 700, and RB211-535E4 
engines. The data presented include material, component life 

cycles, feature life cycles, peak stress, UTS at temperature, peak 

stress/UTS at temperature, and temperature at peak stress for 

critical features.

o Rolls-Royce provided evidence that failure of the HP Shaft System 

is Extremely Remote.

 Prime failure of critical parts is Extremely Remote by 

definition.

 Critical part lifing management continues once the parts 

are in service.

 Rolls-Royce provided an HP Compressor Peak Stress 

Comparison.

 Rolls-Royce provided an HP Turbine Peak Stress 

Comparison.

7. Other questions on EDMS01000175101 and DNS192492 Iss 2 (6 Mar 14).

Para. 5.5.9 of EDMS01000175101 and para. 9.8 of DNS192492 discuss oil fires 

and the likelihood that no fire will stabilize in the area between the HP shaft and 

the IP shaft. Given that the HP shaft geometry and shaft speeds of Package C are 

different from Package A, please clarify what evidence there is that oil collecting 

in the HP shaft area of a Package C engine will not result in a fire in the HP shaft 

area?

o Rolls-Royce provided a detailed explanation for why a fire leads to 

IPT shaft failure. Rolls-Royce showed development and in-service 

events on different engine types support that regardless of different 

HP shaft geometry, shaft speed and air flows, the fire will lead to an 

IPT shaft failure.

8. Other questions on EDMS01000175101 and DNS192492 Iss 2 (6 Mar 14).

Para. 5.5.6 of EDMS01000175101 and para. 9.5 of DNS192492 say that since 

there is no way for the HP shaft (drive arms) to rub directly on the IP shaft, there 

is no threat posed to the HP torque path from contact with the IP turbine shaft. 

Given that the torque path connects to the HPC disc, HPT disc and mini-disc, 

please clarify what experience you have on the effects of IP shaft to disk 

(HPC/HPT/mini-disc) rubbing on the HP torque path?

o Rolls-Royce provided an explanation showing the gap between the 

IPT shaft and all components on the HP shaft system is too big to 

allow any contact of IPT shaft on HP torque path.