Questions on the 707 FDE

[George Carty - HJG]

I've found that the FDE I was using to test my 707 panel (by the way, I've now got the retractable landing light switches working - only the external air unit and altitude alerter are still to be added) was badly deficient (eg when I emptied the centre tank the plane tipped up onto its tail ) when combined with the HJG visual model.

I plan to start again with the current HJG FDEs, but I need to know what characteristics of this FDE are already confirmed realistic. Will just changing the lift table 404 (to set clean stall speeds) and the flap sections of the aircraft.cfg (to set dirty stall speeds) be enough to get fully realistic behaviour, or are other parts of the FDE still deficient (fuel consumption? range? cruise AoA?)

[aerofoto - HJG Admin]

I've always felt the HJG B707/720 models performed quite well .... but there again .... I've unfortnately never had any reference/technical data or manuals for the type with which to make realworld performance comparasons

Mark C
AKL/NZ

[Harerton Dourado - HJG]

I have performance data on the -100B, 720B and 300 (this last one I believe to be quite similar to -400 because they had the same wings, only the engines were different). If any info is needed just ask and I can scan it and share it.

[aerofoto - HJG Admin]

this last one I believe to be quite similar to -400 because they had the same wings, only the engines were different

Actually this "wing thing" is probably a very important consideration with FDE .... because Boeing changed the wing of the civil B707 at least 3 times betweem B707-120 & B707-320C. I guess that would directly impact the stall speeds between the different versions.

The only other considerations I can immediately think of are the P&W JT3C turbojet powered B707-120 would undoubtedly have been realised through this particular aircraft being a bit more gutless than subsequent P&W JT4 turbojet powered B707-138, -220, & -320 versions. Then there was the increased fin height and lower rear fuselage ventral fin later added to B707-320/420 and most later B707 versions to improve lateral stability too. B707-320B/C versions were more powerful again in consideration of their P&W JT3D-3B & D-7 fanjet engines. I guess that performance of B720-A & 720-B would probably be somewhere between B707-320 & 320B .... in terms of power/thrust performance.

If it were possible to reflect little subtleties like these within new FDE's for each of the the current HJG 2006 B707/720 types then that would be a huge improvement .... in my oppinioon.

Whilst all our current B707/720 models seems to fly very well, I have noticed their performance (in terms of speed/acceleration/thrust) seems to currently be "pretty much of a muchness" right throughout the family.

Just a few immediate and casual thoughts/observations on my part .... that's all

Mark C
AKL/NZ

[horse]

Gents.
Will have a look at the problems mentioned today. I have used most of the 707 aircraft in past times and have not encountered the problems you mentioned.

I have a program called " Aircraft Container Manager" that allows me to position all aspects of the model in their correct locations.
Have done the 138 model will have a look at the others soonest.

As for the 400 series, I may be wrong, but from memory and from what I recall from the BOAC Tech School, it was a 200 intercontinental with RR Conway engines. Will see if I can find any of my olde training notes.

Brian.H

[Harerton Dourado - HJG]

In fact the 400 was the same as the 300. The 300 had PW turbojets and the 400 had RR turbofans. The specs I have in the PanAm manual are from the -300 turbojets not 300-B/-C or -B/ADV turbofans.

[horse]

Mark.

Have just read you reply properly. Do you mind if I correct a couple of things.

The original 707-100 and 138 were powered by the P&W JT3B engines, the B series aircraft were powered by the JT3C engine, which was a fanned version of this engine.

The 707-200 and 300 intercontinental and the were powered by the JT4 engine.

The 707-400 had the RR Conway

The 707 -320 series had an upgraded JT3B engine

The original 100 and 200 series aircraft only had a powered assisted rudder system. With the upgrade to the B series engines the rudder system was modified to a fully powered system.

The Ventral fin was added as a British ARB requirement to the 400 series to retain directional control in the event of a 3 engine overshoot as this aircraft only had the power assisted Rudder. The Conway engines rate of acceleration was about a third of that of the P&W's and at high body angles the lower portion of the fin is blanketed by the fuselage, and directional control would have been difficult had the Flight Crew slammed the throttles open quickly, as they did tended to do.

On the 320 series aircraft the Fin height was increased, and a fully powered rudder so the ventral fin was no longer required.

As this is all from memory I may have missed some minor points so please feel free to add or subtract any comment you think I may have overlooked.

Brian.H

[George Carty - HJG]

Fuel Consumption scalars for AIRCRAFT.CFG files (these are twice the lb/hr/lbf SFC values):

P&W JT3C (turbojet): 1.56
P&W JT3D (turbofan): 1.06
RR Conway: 1.26

Also, the tall fin mentioned was in fact the same on all production 707s (it was 'tall' compared to that of the Dash-80). The modification which made it possible to remove the ventral fin on the 707-320B-ADV/-320C was the fitting of full-span leading-edge flaps (which meant more lift - thus a less severe angle of attack in the overshoot) and an improved lift distribution (more stability).

[chris]

Although I am no expert on what 707s came with what engines, I can clarify something regarding the engines themselves, as there seems to be some confusion.

The JT3D is a turbofan, the "D" stands for "Ducted". That is the only P&W in the JT3 series that was a turbofan, the rest were all turbojets. That means the JT3B and JT3C are turbojets, not fans. The JT4 was also a turbojet, albeit a more powerful version of the JT3 turbojets.

Something that may throw people off is seeing something like JT3D-3B, which is not the same as a JT3B. It is a JT3D. The numbers before the dash are the engine model and you cannot abbreviate that or drop any of the digits, or you will be talking about something completely different, and everything after the dash merely shows which version of that model it is, in this case, the -3B variant.

Chris

[aerofoto - HJG Admin]

OK .... just to further clarify B707 aircraft/powerplant variations and other destinguishing structural features.

B707-120 (original short tail and no ventral fin).
P&W JT3C-6 turbojets .... possibly water injected but I'm not sure.
Fuselage length 144ft 6in. Wingspan 130ft.10in.

B707-120B (tall tail with ventral fin added).
P&W JT3D-1 or JT3D-3 fanjets (often also referred to as turbofans) .... depending upon airline selection. Fuselage length 144ft 6in. Wingspan 130ft.10in.

B707-138 (original short tail and no ventral fin).
P&W JT3C-6 turbojets .... with water injection. These aircraft were a shortened version of B707-120 (reduced by 10ft) designed especially for QANTAS Airways. Only the first 6 of these aircraft delivered to QANTAS (VH-EBA thru -EBG .... all 1959 deliveries) were short tailed and JT3C-6 turbojet powered. The remaining 6 138's delivered to QANTAS between 1961 and1964 (VH-EBH thru -EBM) were all tall tailed, ventral finned, and powered by P&W JT3D-3B fanjets and designated "B707-138B". All 6 original QANTAS 138's were then also converted to 138B's during the early 1960's. Fuselage length 134ft 6in. Wingspan 130ft.10in

B707-220 (original short tail and no ventral fin).
P&W JT4-A3 turbojets .... this version was designed as a "HOT AND HIGH" aircraft for Braniff International. Only 5 were ever built and these also later featured what became the standard B707 tall tail with ventral fin. None of these aircraft were ever re-engined with fanjets/turbofans. Fuselage length 144ft 6in. Wingspan 130ft.10in

B707-320
P&W JT4A-3, JT4A-9, or JT4A-11 turbojets .... depending upon airline selection. This version featured an 8ft 5in fuselage stretch for what became the definitive B707 fuselage length of all subsequent B707 versions. A few ("very few") of the initial production versions of B707-320 entered service with the short tails (AIR FRANCE) and without the ventral fins but were later added to all. Fuselage length 152ft 11in. Wingspan 142ft.5in

B707-320B (tall tail with rear fuselage ventral fin).
P&W JT3D-3 or JT3D-3B fanjets .... depending upon airline selection. This version also featured increased wingspan. Fuselage length 152ft 11in. Wingspan 145ft.9in

B707-320C (tall tail).
P&W JT3D-3, JT3D-3B, or JT3D-7 fanjets .... depending upon airline selection. Equipped with forward fuselage maindeck freight door. All were tall tailed but some aircraft never featured the rear fuselage ventral fin. Fuselage length 152ft 11in. Wingspan 145ft.9in

B707-420
RR CONWAY 508 fanjets.
Apart from its powerplant the -420 was otherwise identical to the -320. It was the first B707 version to fly wth the tall tail and ventral fin added which became standard features of "definitive B707 verions" (-320B/C). It was also the first 707 version to fly with fanjet engines. Again a few ("VERY VERY FEW") initial production versions of B707-420's entered service with short tails and without ventral fins (AIR INDIA) .... but again .... these "were" later added after the Braniff accident and British COA requirement. Fuselage length 152ft 11in. Wingspan 142ft.5in

B720 (sometimes also referred to as "B720-A").
P&W JT3C-7, or JT3C-12 turbojets .... depending upon airline selection. Tall tail and ventral fin equipped with 8ft.4in reduction in fuselage length from that of B707-120. Fuselage length 130ft 11in. Wingspan 130ft.10in.

B720-B
P&W JT3D-1, or JT3D-3 fanjets (derated) .... depending upon airline selection. Tall tail and ventral fin equipped with 8ft.4in reduction in fuselage length from that of B707-120. Fuselage length 130ft 11in. Wingspan 130ft.10in.

These details are all quoted from the "GOSPEL ACCORDING TO MR BOEING" .... hope it helps clear up any further confusion

I might sometime in the future whack together an illustrated feature about all these B707 versions for our "HISTORY PAGE" here on this forum

Mark C
AKL/NZ

[George Carty - HJG]

Military aviation enthusiasts may also be interested to know the USAF designations for these engines. The JT3C has the military designation of J57, the JT4A is also the J75, while the military JT3D is known as a TF33.

By the way, my modified -320B/C and -420 flight models are now sorted - only the panel needs to be finished!

[aerofoto - HJG Admin]

By the way, my modified -320B/C and -420 flight models are now sorted - only the panel needs to be finished!

Sound g-r-e-a-t George

Many thanks for your dedication to this task .... really appreciated

Mark C
AKL/NZ