Although P&W developed a fix, I think it was still a problem during the initial period of 747 service. I think there were other problems also. Even Pan Am's inaugural 747 flight JFK-LHR in January 1970 was delayed about 3 hours when they had to substitute another aircraft for the one planned when the first one developed engine problems.
Not sure if it involved the same problem as the one mentioned in the Flight article, but if memory correct another issue was engine overheating when starting if the wind was blowing in the wrong direction.
747classic From Netherlands, joined Aug 2009, 1781 posts, RR: 11 Reply 3, posted (3 years 4 months 2 weeks 2 days 21 hours ago) and read 6128 times:
Quoting Faro (Thread starter): technical terms, why was the engine problematic on the very first 747's in the 1970's and how did P&W remedy this?
- 1) Under powered ,delivered not enough thrust for the ever increasing MTOW of the 747, to get maximum thrust HP turbine section was operated at limits.
- 2) Very sensitive for tail and X-wind, especially during starting, causing hot starts or stalls.
- 3) Ovalisation of the engine casing during T/O, causing blade rubbing and loss of efficiency.
- 4) In general very stall sensitive during power transitions, don't put the power levers suddenly to idle.
- 5) Damaged HP turbines, caused by failing rivets in blade-retaining plates in early engines.
Remedies :
- 1) Product development, slowly increased thrust from 43.500 lbs, first via addition of water injection in the dash -3A engine. Then further increase possible via improved HP turbine blades in dash 7, 7W, 7A, 7AW, 7F and finally maximum 50.000 lbs in dash 7J with single cristal HP turbine blades with improved cooling. Two improved variants (with different type certificate) with more thrust were developed to counteract the GE and RR engines offered from 1975. First the -70 and -7Q were developed, the final (at last matured) engine was the dash -7R4 series.
- 2) Small improvements made starting not so demanding, but still the engine was/is very tricky to start in tail wind conditions. (valid for all dash -7 versions up to -7J.)
- 3) Was remedied by a thrust yoke, to spread the forces applied between the pylon and engine better.
- 4) Addition of ARS (automatic recovery system) in fact extra (3.5) bleed valves dumping air, when an impending stall condition was sensed. During reverse RABS (reverse actuated bleed system) was built in to release air from the engine in case of impending stall.
- 5) Improved rivets installed.
Sources : Jet and Turbine Aero Engines by Bill Gunston and own experience on 747-200/ JT9D-7(W) aircraft from 1978 till 1991.
Faro From Egypt, joined Aug 2007, 1443 posts, RR: 0 Reply 4, posted (3 years 4 months 2 weeks 2 days 8 hours ago) and read 5982 times:
Quoting 747classic (Reply 3): - 1) Under powered ,delivered not enough thrust for the ever increasing MTOW of the 747, to get maximum thrust HP turbine section was operated at limits.
- 2) Very sensitive for tail and X-wind, especially during starting, causing hot starts or stalls.
- 3) Ovalisation of the engine casing during T/O, causing blade rubbing and loss of efficiency.
- 4) In general very stall sensitive during power transitions, don't put the power levers suddenly to idle.
- 5) Damaged HP turbines, caused by failing rivets in blade-retaining plates in early engines.
Thanx for the detailed reply. The JT9D was very much a pioneering endeavour and in a way it was normal that it had so many problems. Happy thing is (IIRC), none of these problems ever gave rise to accidents.
MarkC From United States of America, joined Apr 2006, 259 posts, RR: 0 Reply 5, posted (3 years 4 months 2 weeks 2 days 7 hours ago) and read 5974 times:
I worked for a guy (now retired) who had a framed copy of a memo from 1970. It was from the president of NWA to the president of PW, highly sarcastic, and complained about the fact that stage 1 HPT blades were lasting only 500 hours.
Starlionblue From Hong Kong, joined Feb 2004, 15870 posts, RR: 66 Reply 6, posted (3 years 4 months 2 weeks 2 days 6 hours ago) and read 5955 times:
The engines were by far the biggest problem with the 747 program. Joe Sutter jokingly asked the P&W guys for a scrapped JT9D to be mounted on a plinth outside his house. The reason? "So I can go out every morning with my gun and shoot the damn thing just to make me feel better".
"There are no stupid questions, but there are a lot of inquisitive idiots." - from Citadel by John Ringo
Northwest727 From United States of America, joined Jul 2005, 491 posts, RR: 1 Reply 7, posted (3 years 4 months 2 weeks 1 day 1 hour ago) and read 5769 times:
In addition to what you stated, I've read to that Boeing themselves redesigned the engine mounts for the JT9Ds on the early 747's...this was to minimize engine "oval-ization" at high thrust settings. I will try to find out more on this.
747classic From Netherlands, joined Aug 2009, 1781 posts, RR: 11 Reply 9, posted (3 years 4 months 2 weeks 4 hours ago) and read 5602 times:
The inverted Y-shape thrust yoke was actually designed by P&W, after a terrible row between Boeing and P&W about this engine-pylon interface problem. Pratt tried first to blame Boeing for it.
At last Pratt designed it, with help of a Boeing computer program, developed for the stress predictions in the 727 tail-fuselage, to calculate the solution of this JT9D ovalisation problem.
Source : Wide Body, The triumph of the 747 by Clive Irving , page 337 and further.
WA707atMSP From United States of America, joined Oct 2006, 2038 posts, RR: 13 Reply 10, posted (3 years 4 months 1 week 4 days 2 hours ago) and read 5331 times:
Quoting Faro (Reply 4): Thanx for the detailed reply. The JT9D was very much a pioneering endeavour and in a way it was normal that it had so many problems. Happy thing is (IIRC), none of these problems ever gave rise to accidents.
There were several very close calls, however. In Aug 1970, an Air France 747 taking off from Montreal suffered an uncontained engine failure. Rather than dumping fuel, the aircraft's pilots chose to burn off fuel by flying to JFK for an emergency landing. A similar incident, involving an American Airlines 747, took place near SFO in Oct 1970. If either of these uncontained engine failures had resulted in key control lines, or a fuel line, being severed, then there might have been a serious accident.
Faro From Egypt, joined Aug 2007, 1443 posts, RR: 0 Reply 11, posted (3 years 4 months 1 week 2 days 8 hours ago) and read 5169 times:
Quoting WA707atMSP (Reply 10): In Aug 1970, an Air France 747 taking off from Montreal suffered an uncontained engine failure. Rather than dumping fuel, the aircraft's pilots chose to burn off fuel by flying to JFK for an emergency landing.
Is this because it was an outboard engine? Is this standard operating procedure in such cases?
747classic From Netherlands, joined Aug 2009, 1781 posts, RR: 11 Reply 12, posted (3 years 4 months 1 week 2 days 6 hours ago) and read 5152 times:
Quoting WA707atMSP (Reply 10): There were several very close calls, however. In Aug 1970, an Air France 747 taking off from Montreal suffered an uncontained engine failure. Rather than dumping fuel, the aircraft's pilots chose to burn off fuel by flying to JFK for an emergency landing.
Fully correct,
To be exact, it was 747-128 F-BPVD , scheduled from Chicago (ORD) to Paris Orly (ORY), with an intermediate stop in Montreal Dorval (YUL). During Climb out from Montreal engine #3 had an uncontained engine failure and the aircraft diverted to New York (JFK) on Aug-17-1970, see :
The Flight crew decided not to dump fuel in view of uncertainty about the damage, caused by the engine (not visible good enough from the cabin.) and decided to burn off the fuel and diverted to JFK (better engine change and structural repair possibilities ?)
IMO it would also have been possible to dump fuel from the left hand side dump pipe only. (reduced dump rate), but the report doesn't mention any vibrations or other problems after the incident, so diverting to JFK was a perfect possibility and the crew decided not to pressurize the dump system.
The cause of the engine failure was a total separation of the second-stage turbine disk outer rim, which ruptured the engine high-pressure turbine case, and caused massive deformation of the adjacent engine structure. After investigation it showed that the disk and rim were not properly assembled at the P&W shop after modification of the rivets in the first turbine stage (one of the weak points of early engines as mentioned before) and other modifications at the second stage.
Wow. Any comment after that is going to be a bit close to the "Apart from that Mrs Lincoln, did you enjoy the play".
My first 747 was a BA flight to Chicago in Sept 1970 and we went over Greenland in glorious weather so watching the ice took my mind off #3 and #4 that were all too clearly visible out of the window and I was aware that the engines were not quite, well, er mature!!
747classic From Netherlands, joined Aug 2009, 1781 posts, RR: 11 Reply 14, posted (3 years 4 months 1 week 2 days 4 hours ago) and read 5123 times:
Quoting WA707atMSP (Reply 10): A similar incident, involving an American Airlines 747, took place near SFO in Oct 1970.
I did some research in this accident.
It happened at Sept-18-1970 with a 747-121 (PAA) operated by AA with registration N743PA.
The whole story is mentioned here : www.airdisaster.com/reports/ntsb/AAR71-07.pdf
Most striking is the amount of engine failures that happened in those pioneering years.
WA707atMSP From United States of America, joined Oct 2006, 2038 posts, RR: 13 Reply 15, posted (3 years 4 months 1 week 1 day 22 hours ago) and read 5062 times:
Quoting 747classic (Reply 14): Quoting WA707atMSP (Reply 10):
A similar incident, involving an American Airlines 747, took place near SFO in Oct 1970.
I did some research in this accident.
It happened at Sept-18-1970 with a 747-121 (PAA) operated by AA with registration N743PA.
The whole story is mentioned here : www.airdisaster.com/reports/ntsb/AAR...7.pdf
Thank you for finding the NTSB report for this incident.
It's scary to read that at one point flames were burning above the wing from the failed engine. The crew did a remarkable job of landing this aircraft safely, because of the damage to the 747's hydraulic system.
Soon7x7 From United States of America, joined May 2006, 2798 posts, RR: 14 Reply 16, posted (3 years 4 months 1 week 1 day 15 hours ago) and read 4983 times:
Slightly off topic but remember early 747's also blowing a lot of tires on landings till the manufacturers redesigned tires...also 747 landing gears redesigned 9x...j
Okie From United States of America, joined Jul 2003, 2355 posts, RR: 3 Reply 17, posted (3 years 4 months 1 week 1 day 14 hours ago) and read 4971 times:
Quoting Soon7x7 (Reply 16): Slightly off topic but remember early 747's also blowing a lot of tires on landings till the manufacturers redesigned tires...also 747 landing gears redesigned 9x...j
I do not know if it was an old pilots tale but I remember that the story went that Boeing was doing a demo flight for a prospective customer when on take off one the the wheel assemblies fell off and bounced down the runway.
Soon7x7 From United States of America, joined May 2006, 2798 posts, RR: 14 Reply 18, posted (3 years 4 months 1 week 1 day 14 hours ago) and read 4968 times:
I heard that one as well...even happened at MDW with a WN and the tire blew through the wall hitting a car...747's sure had their growing pains...but what a reliable ship she turned out to be...thats why I believe after a slow start in sales the 747-8 will take off...I read 8 have been ordered for private use already and 12 787's...j
Brons2 From United States of America, joined Sep 2001, 2969 posts, RR: 5 Reply 19, posted (3 years 4 months 1 week 1 day 10 hours ago) and read 4942 times:
For how long did PW have exclusivity on the 747?
What other planes used the JT9D? I can think of the DC-10-40 and early 767's for two.
Firings, if well done, are good for employee morale.
747classic From Netherlands, joined Aug 2009, 1781 posts, RR: 11 Reply 20, posted (3 years 4 months 1 week 1 day 9 hours ago) and read 4923 times:
Quoting Brons2 (Reply 19): For how long did PW have exclusivity on the 747?
The first 747 aircraft flown, with other than P&W engines installed, was the prototype 747 flown re-engined with 51.000 lbs. General Electric CF6-50D engines with a first flight on 26 June 1973.
The first re-engined military 747 was the third E4A, serial number 20684, L/N 232, registration 74-0787, first flight at 06 June 1974, was handed over to the USAF at 15 Oct. 1974 with 52.500 lbs.General Electric CF6-50E engines.
The first military new built 747 was a E-4B, serial number 20949, L/N 257, registration 75-0125, first flight at 29-April-1975 with CF6-50E engines.
The first civil 747 was a KLM 747-206B, serial number 21110, L/N 271, registration PH-BUH, first flight at 19-Okt-1975 also with GE CF6-50E engines.
The first RR powered 747 was a BA 747-236, serial number 21238, L/N 292, registration G-BDXA, first flight at 03-Sept-1976 with 50.000 lbs. RB211-524 engines
Quoting Brons2 (Reply 19): What other planes used the JT9D? I can think of the DC-10-40 and early 767's for two.
Correct and also A300-B4-620 and A310-200/300 aircraft used JT9D-7R4 engines.
Sources : Boeing, 747 Design and Developement since 1969 by Guy Norris and Mark Wagner
747 and A300/310 TCDS
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