707 Engine Performance

[George Carty - HJG]

I've noticed that the N1 RPM on the HJG 707s (my FDE editing so far hasn't touched the engine tables yet), setting throttles to maximum can give N1 readings as high as 111%. Is this behaviour realistic?

How much attention to detail was given in programming the 707 engine behaviour in the AIR file? I would like to know so I can determine if I can improve the EPR gauges on the panel (I calculate EPR as the FS token variable is rubbish).

[trevorselby]

This would be correct. The old JT3D-3B had an N1 max of 110.8% and a N2 of 106.2

The takeoff EPR for a 320C is 1.82 at sea level at std. temp. This EPR corrosponds to a N1 of 107.6 %.

Iam still using FS2002 and have an excellent FDE by Ron Freimuth which gives a pretty accurate readout on your gauges. I've made some minor changes to suit match the HJG models. I been using it more a number of years now with your panel. EPR at cruise is pretty accurate as well as the FF and general performance.

Maybe you would like to look at it and adapt it for FS2004.

Trevor

[Harerton Dourado - HJG]

Hi,

Yes the EPR readings need to more accurate, as EPR is the main engine parameter when flying the 707.

Maybe this issue could be addressed at gauge programming. But this woud require the determination of the EPR/N1 relation or EPR/"other known parameter available in FS". George, how do you approach this issue?

As for Ron Freimuth FDE, if it's the one included in P. Goulding panel, I remember having some trouble at landings, the acft would float at the flare. But probably this could be a pilot problem...

[chris]

In the real world, at least on older aircraft without any computer controlled overspeed protection, like the 707, 727 and non-70-series DC-8's, if you "firewall" the throttles, you will overspeed the engines beyond their maximum allowed speed, which oddly, is almost always rated over 100%, so 111% is not so far out of line, and is actually most likely lower than you'd get should you be brave enough to try with the real thing.

The throttles aren't rigged to provide a certain "maximum" from the engine when positioned all the way forward. Rather, the throttles are rigged at an intermediate "part-power" position, with the engines putting out a certain rpm and epr at that position, specified in the maintenance manual. Once all the throttle cables are rigged, the aircraft is taken to a run-up area and a "trim run" is performed, and the fuel controls on each engine are adjusted to obtain the correct parameters.

[Harerton Dourado - HJG]

Great post Chris!

[garryrussell]

Chris

Thanks for that

A lot of useful information and an explanation of the meaning and adjustments of throttle settings in an easily understood piece.

Garry

[horse]

Gents.

The above applies to the P&W engines but not for the RR engines.
With the RR Conway the N1, N2, Power and EGT were all governed and on most take offs the throttles were pushed all the way open.
On high altitude hot T/O's it may be EGT that was the governing factor, out of Brisbane ( Australia ) on a nice cool winters morning it would be the power limiter.
The British concept at that time was a tad different to that of the US engine manufacturers in that there was a minimum power for T/O and anything above that was a bonus. I believe that the performance figures for the aircraft were calculated on the minimum T/O power which in the case of the Conway 508 was 17500 lbs. The power limiter restricted power to 19000 lbs.
The rate of acceleration of the Conway was far better than its US counterparts.
The average figure from idle to stabilised full power was 4.5 seconds.
The P&W JT3D in the 707 was in the order of 10 to 15 sec from idle to the part power stop. ( I know what is the part power stop ). It was a Throttle stop fitted to the fuel control unit for power adjustments as an accurate reference point.
Another bit of trivia. When doing these checks on the Conway engine the throttle was advance quite quickly, and I have never had and engine surge or stall. To do the same with the P&W would cause some very load explosive like sounds, and at times some evidence of smoke and flame from either or both ends of the engine.

[aerofoto - HJG Admin]

Real interesting stuff .... "CHRIS" & "HORSE" !

To do the same with the P&W would cause some very load explosive like sounds, and at times some evidence of smoke and flame from either or both ends of the engine.

Here at Auckland (AKL/NZAA) in the past, I've witnessed surges a couple of times on UNITED's old B747-100's .... when they first flew them here during the mid 1980's.

It was "a hell of a bloody BANG" .... like a cannon going off and echoing all round the airport environment .... and with a show of big flames pouring out the tail pipes of the engines and white swirling smoke/vapour inside the intakes to boot.

Not good for the aircraft/engines .... but .... quite a spectacular sight/experience indeed.

Mark C
AKL/NZ

[garryrussell]

I'm a bit like that after a curry!

Garry

[chris]

Horse, thanks for the informative reply!

Garry, please spare us any further details regarding your intolerance to curry!

I suppose I should have included the fact that I was talking about older P&W engines (JT3, JT3D, JT8D, JT9D). Having worked exclusively for United Airlines during my "aviation career", I have little knowledge of RR engines, although I appreciate any snippets of information on the subject.

Mark, those 747 "classics" we had were in rough shape for years. They'd leak and burn 7-10 quarts of oil (per engine) on a 10 hour flight. They finally went through the whole fleet and brought the engines up to proper standards, and reduced the useage to 2-4 quarts on the same 10 hour flight. The stall margin was also improved, so those compressor stall "backfires" were far less frequent after that.

Ironically, the "new and improved" 747-400 with the P&W engines had similar stall margin problems once they got some miles on 'em.

Chris

[George Carty - HJG]

Does anyone here know the typical takeoff EPR for Conway, JT3C and JT4A engines? Was it similar to that for a JT3D?

[chris]

Although this info is for the DC-8, they should be fairly close to what's in the 707 takeoff EPR tables. According to my 1968 United Airlines DC8 flight manual:

At 0 feet altitude @29.92 in/hg at 60 degrees F,

JT4A-3 static takeoff EPR (with anti-ice bleed off) is: 2.48

JT3D-1 @40-80 knots, takeoff EPR: 1.82
JT3D-3 @40-80 knots, takeoff EPR: 1.85
JT3D-3B @40-80 knots, takeoff EPR: 1.86

Max rotor speeds:

JT4A n1=102.6% (6950rpm), n2=103.0% (8960rpm)
JT3D-1 n1=109.9% (6800rpm), n2=105.6% (10200rpm)
JT3D-3 n1=109.9% (6800rpm), n2=106.2% (10250rpm)
JT3D-3B n1=110.8% (6850rpm), n2=106.2% (10250rpm)

I have the JT3C info as well in an older manual, but I'll have to dig it out.

Chris

[aerofoto - HJG Admin]

Does anyone here know the typical takeoff EPR for Conway, JT3C and JT4A engines? Was it similar to that for a JT3D?

George .... "Matt ZAGOREN" put together a very good package containing AOM engine performance data applicable to all weight/temperature/altitude variations for each of the following powerplants

P&W JT4A-3
P&W JT3D-3
P&W JT3D-3B
P&W JT3D-7

Although this data is for DC8, I suspect the EPR values may share some commonality with B707 too. This package is available on AVSIM or FLIGHTSIM (or both). The filename is

dc8perf.zip

"ZAGOREN" also put together a similar B707 specific package too, but, I don't think it contains AOM engine performance data for the entire B707 series. Anyway .... the filename for this package is

b707perf.zip

"Jim HALINDA" similarly compiled a very useful set of rare AOM data for RR CONWAY 509 engines and DC8-40. Again this may share some basic commonality with B707 and RR CONWAY 508 engines .... as ballpark figures. The AVSIM filename is

dc8perfcharts.zip

The abovementioned downloadable files range from only 2-3 MB each in size.

In the meantime: Chris .... is there any way some of us could get hold of AOM data for P&W JT3C-6 series engines directly from you ?

Hope you don't mind me asking, but, these and the CFM's are really the only engine reference data I'm currently lacking.

Mark C
AKL/NZ

[jimhalinda]

Here's my two cents:

Although the manual (from Air Canada) that I uploaded does include a DC-8-40 chart for Minimum EPR at Static Take-off Thrust, the procedures section does not always use EPR as a guide. Further, you can see that procedures for the [40] are not the same as for the [50] and [60]. For example:

The pilot flying the airplane will advance the throttles approximately 1 1/2", wait for engines to spool up to approximately [40] 7,500 N2, [50/60] 75% N2 then open them smoothly and evenly to take-off power within 4 - 5 seconds.

...I assume take-off power is an EPR value for all types? And then later:

NO NOISE ABATEMENT:

At 1,500 feet AGL pilot flying calls and hand signals "CLIMB THRUST". The other pilot sets climb thrust, i.e. [40] 9,500 N2, [50/60] climb EPR, and performs UPLATCH CHECK.

NOISE ABATEMENT:

At 1,500 feet AGL, or when sensitive area is reached whichever occurs first, or on timing as advised by the Second Officer, the pilot flying calls and hand signals "NOISE ABATEMENT THRUST". The other pilot within 10 seconds sets [40] 2.1 EPR or less consistent with a minimum rate of climb of 500 fpm, [50/60] Climb EPR, and performs the UPLATCH CHECK.

...Interesting that for noise abatement, a specific EPR setting is used for the 40, but with no noise abatement they just say 9,500 N2.

...and finally in the climb:

Maintain climb thrust. [40] Check at frequent intervals and reset to 9,500 N2 as required. [50/60] During climb through each 5,000 feet, the pilot flying calls the RAT and the Second Officer responds with the correct EPR for the RAT and altitude.

Also, regarding CFM-56s, I posted a question about values used on the old forum, and John Detrick gave me the following reply:

"a max power takeoff setting will normally be around 90 to 92 % N1, a reduced power takeoff will be in the ballpark of 85 %N1. Your initial climb power settings will be in the area of 87 to 88% N1 with that setting increasing as altitude increases, with a setting of around 93 to 94 %N1 at altitude (FL 330 or so). Of course these are just generic ballpark figures that will work with the sim. The real values change a bit with variations in temperature and altitude"

Regards,

Jim

P.S. In addition to the performance charts, I later uploaded four full chapters from the Air Canada DC-8 manual (courtesy Herman Kreimes), the file is on Avsim called dc8manual.zip . This includes the procedures I quote above.

[chris]

Mark,

Unfortunately, the only manual I have with me that has any info is my '68 United DC-8 flight manual, which sadly does not have any JT3C information. I may have some information in an older manual, but it is elsewhere, so give me a couple days on that. The one other systems manual I have here does have JT3C information, but no flight data or charts in regards to specific EPR settings for takeoff, etc.

I myself would also like to get my hands on a DC-8 70 series CFM-56 AOM. I may have to look into that...