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B747-100 engine problems on early versions

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B747-100 engine problems on early versions

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Old 18th Jun 2008, 15:14
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B747-100 engine problems on early versions

Hi All

I have heard that on the early 747's there was a problem with the engines when taxiing or at stand stalling / cutting out.

I am trying to understand what the problem is, is it wind blowing into the rear of the engine blowing out the fame cans (unlikely I would have thought) or uneven burning inside the flame cans ?

speaking more generally, was there any other 'teething problems' with early 747's that were rectified on subsequent versions ?

Since the 747 took aviation in a new dimension I would imagine that there must have been a few hurdles to overcome.

thanks in advance.

RD
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Old 18th Jun 2008, 17:35
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Bleed system problems. On our -100 course we were taught four different bleed system configurations - and they were the ones that worked (more or less)! The compressor had either had more air than it could handle or not enough; so it was prone to compressor stall: Getting the balance right seemed to have been a matter of trial and error by P&W in the early days of the JT9
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Old 18th Jun 2008, 20:12
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JT-9D fan cases that warped and got out of round was a huge issue early on, as well as very slow starting, rapid performance deterioration, etc., etc.
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Old 18th Jun 2008, 20:36
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I too understood that the fan housing going out of circularity and the fan scraping it was a key early issue on JT9Ds. The maiden commercial flight in January 1970, Pan Am from JFK to London (already delayed a month), got this on startup and they had to transfer to a backup aircraft which meant they were 4 hours late at London.

Boeing initially produced more 747s than P&W could keep up with working engines for; I remember visiting Everett in late 1969 and seeing a sizeable fleet parked outside with concrete blocks suspended from the engine supports.

Of course the Pan Am skippers in those days had started out on Wright-engined DC7s and Constellations, where if you made any trip across the Atlantic without shutting down an engine you were doing well !
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Old 18th Jun 2008, 21:18
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Of course the Pan Am skippers in those days had started out on Wright-engined DC7s and Constellations, where if you made any trip across the Atlantic without shutting down an engine you were doing well !

And of course we won't even think about the lovely old Stratocruiser!
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Old 19th Jun 2008, 01:46
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And of course we won't even think about the lovely old Stratocruiser!
Stratocruiser.
I flew these for awhile, and never had engine problems....so long as one did not run out of oil.
DC-7...a different story altogether.
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Old 19th Jun 2008, 03:21
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diddy1234, as blacksheep has so rightly pointed out, P&W had major problems with the JT's, so much so that the 747 was nearly grounded for good. Good for RR in the end though!!
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Old 19th Jun 2008, 10:52
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Not only fan cases going out of round, the engine had a habit of bending in the middle There was a mod to fit the yoke assy. between the intermediate case and the rear thrust mount.
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Old 19th Jun 2008, 11:03
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Ahha! the good old JT9d-3a anyone for a description of the BLEEDS system?
3.0 bleed ring.
3.5 bleed valves (x4)
4.0 bleed vavles (x2) more commonly referred to as the 15th stage.
8th stage customer bleed.
15th stage customer bleed.
7th stage bearing pressurisation bleed.
Now the above bleed valves worked in various combinations of:-
Start bleeds.
Tandem bleeds.
Surge bleeds.
Reverse bleeds.
It was not uncommon for the early engines to stall on a accel. so a 'bodie tube' was fitted between the (IIRC ) the 3.0 bleed actuator and the lower left 3.5 bleed valve controller.
JT9d-7a/ah/cn gradually improved and the 15th stage bleed valves were removed and then one of the 3.5 bleed valves went as the design of the hp compresor improved.
Even the later JT9d-7q and the -r4g2 had stall problems notibly affecting the fan. N2 reset solenoid upped the fuel flow to compensate
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Old 19th Jun 2008, 12:24
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Bleedin' 'ell! Ahem, sorry...
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Old 23rd Jun 2008, 20:23
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The initial poster asked about other problems. I seem to recall that early Pan Am aircraft had wiring problems which impacted on passengers - reading lights not working, that sort of thing (if my memory serves me well; after all, this was more than 38 years ago!). Perhaps other operators' aircraft suffered similarly (though with BOAC's on the ground for so long they, presumably, had the time to put things right!).
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Old 25th Jun 2008, 14:06
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In early manuals supplied to me prior to ground school, the -3's had a nasty tendency to flame out at the top of climb due to surge bleed valve problems at power reduction. The 7A was a big improvement I gathered. As engineer, I would always place the ignitors on anyway, pull the power back slowly, and then turn the ignitors off. Unnecessary, yes. But I had a classmate who scattered traffic below due to his belief that suction fuel would work as a backup to crossfeed closed and fuel pump off. He was a civil engineer in a former life and believed without question the engineering spec of the engine. What he didn't appreciate was the fact that on old -100's things didn't perform to original spec. While that design still functioned well under 10,000 feet, it was not going to work out of 15,000 on that bird! He was in an argument with the mechanic on what the engine was capable of. He lost that argument.

Of course, he was let go.

I can testify though that the fuel suction actually works good in the pattern. Don't ask how I know......

Cheers
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Old 25th Jun 2008, 21:24
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I seem to recall that in the early days of BOAC's 747 ops that crews were brought into the sim quite regularly to practice 4 engine landings such were the number of engine shutdowns at the time!
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Old 26th Jun 2008, 05:57
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arem, very good.

So whats worse a three engined Lockheed Constellation or an early 747 ?

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Old 26th Jun 2008, 08:21
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Most of BOAC engine shutdowns occurred with other operators airframes!
We were on strike for a period during early 747 introduction and such was the
-3 attrition rate that BOAC 'leant' their engines to others to overcome shortages. A profit was made,I believe, with many of the early BOAC arrivals sitting on the aprons with concrete blocks hanging on the pylons!
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Old 27th Jun 2008, 08:04
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Those early BOAC 747 flights to JFK often failed to achieve their assigned levels by the Shanwick boundary.
I recall Shanwick requiring one of them to read out each hundred feet of altitude as it painfully clawed its way upward. When it triumphantly reached its level there was a round of cheering from other aircraft on the frequency, whereupon the Speedbird immediately began counting down again........
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Old 27th Jun 2008, 14:52
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A sign of the times, discussing the JT9d on the 'Aviation History and Nostalgia' forum.
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Old 27th Jun 2008, 15:10
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I can attest to the accuracy of POHL's statement regarding BA making money with concrete blocks for engines. At TWA we were changing them like underwear and if it wasn't for BA at LHR providing spares TWA/Pan-AM would have been off the Atlantic. We used to fifth pod a lot and it wasn't unusual to drop the fifth pod then turn around and hang it on the aircraft that brought it in because it had lost one inbound. I'm surprised that in any discussion of the idiosyncrasies of the early Jt9D, that the infamous EVC "Wash and W!nk" procedure hasn't come up. When TWA had hung/slow starters we'd open the tins, heave a bucket of WD40 over the compressor case so the EVC link arms got lubed, then some junior mechanic(me) would vigorously excercise the EVC drive bellcrank wi' a bleeding great crowfoot wrench and breaker bar and - voila - turning four.
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Old 27th Jun 2008, 15:37
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Yup! We used to do the same but with Univis P38 in a garden sprayer Mind you the amount of oil that was on the outside of the engine I'm suprised they needed lubing!
Later on it was wintertime fan case wear and summertime EGT limited shortfall
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Old 27th Jun 2008, 15:39
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Good times............good times.........
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