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Phantom FG.1 modifications


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Peter Caygill is referring to the leading edge flaps that were enlarged and incorporated BLC. as did the drooped ailerons (to 16.5 degrees). The reduced anhedral on the slotted tailplane was only a matter of half to one degree (from memory).

Dennis

I must confess that I was under the impression, when I posted the above, that the reduction in anhedral on the F-4K was generally known. My information came from a Management Course that I did at HSA Brough in early '78 where I was, to be honest, a somewhat reluctant student as I was still trying my damnedest to get back to the Civilisation and the Harrier Fleet. My posting to Phantoms following promotion seemed, at the time and still does, a step back to the stone age.

I recently re-discovered my notes, both hand written and printed issues, gathering dust and cobwebs in the loft so I'll quote relevant bits from them.

"Tailplane (FG1):- anhedral reduced by .25 -.75 degrees to increase area, reduce efflux effect on cat launch and increase authority on carrier landing (heavier aircraft as per F-4J), FGR2 as per norm"

"BLC:- Blown flaps on FG1 only - cuts out at 30 degree deflection; 80% on leading edge, 20% on flaps when on; slits 0.035" over 70% of surface, 0.0015" on 30%"

"L/E flaps - inboard locked shut (helps t/p) but hinges down - maint"

"Beefed up main landing gear (J, K and M)"

"Slotted stab. Designed at Brough (MDD/HSA joint venture) Built at Preston, developed from Buccaneer tailplane blow - reduces tailplane stall."

"ECP's (HSA/MDD) on F-4K applied to F-4J (blow, t/p etc)"

"HSA Brough - Design Authority"

We were also given a talk by a MacDonald Douglas Engineer who was one of 50 or so MDD staff permanently based at Brough to advise and also follow developments. He fully acknowledged the help given by HSA and especially at Brough in developing the "British Phantom" and that the ECP's discussed between the two Companies were happily incorporated by MDD into the F-4J as both Navies had similar requirements in certain areas. According to my hand written notes, he also acknowledged that the F-4E benefitted from the development of the slotted stab even more as the CofG on the E had moved forward due to the fitting of the Vulcan gun and it had to retain a large tailplane area for manoeuvre at supersonic speed where the mainplane CofP has shifted aft

The notes go into a lot more detail and a lot of it concerns paperwork, which I ended up doing for six years thanks to the constant stream of modifications, upgrades (especially after the ex 892 aircraft came to Leuchars), "insisted" upon by Brough.

Never did get back to Civilisation.

DR

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I must confess that I was under the impression, when I posted the above, that the reduction in anhedral on the F-4K was generally known. My information came from a Management Course that I did at HSA Brough in early '78 where I was, to be honest, a somewhat reluctant student as I was still trying my damnedest to get back to the Civilisation and the Harrier Fleet. My posting to Phantoms following promotion seemed, at the time and still does, a step back to the stone age.

I recently re-discovered my notes, both hand written and printed issues, gathering dust and cobwebs in the loft so I'll quote relevant bits from them.

"Tailplane (FG1):- anhedral reduced by .25 -.75 degrees to increase area, reduce efflux effect on cat launch and increase authority on carrier landing (heavier aircraft as per F-4J), FGR2 as per norm"

"BLC:- Blown flaps on FG1 only - cuts out at 30 degree deflection; 80% on leading edge, 20% on flaps when on; slits 0.035" over 70% of surface, 0.0015" on 30%"

"L/E flaps - inboard locked shut (helps t/p) but hinges down - maint"

"Beefed up main landing gear (J, K and M)"

"Slotted stab. Designed at Brough (MDD/HSA joint venture) Built at Preston, developed from Buccaneer tailplane blow - reduces tailplane stall."

"ECP's (HSA/MDD) on F-4K applied to F-4J (blow, t/p etc)"

"HSA Brough - Design Authority"

We were also given a talk by a MacDonald Douglas Engineer who was one of 50 or so MDD staff permanently based at Brough to advise and also follow developments. He fully acknowledged the help given by HSA and especially at Brough in developing the "British Phantom" and that the ECP's discussed between the two Companies were happily incorporated by MDD into the F-4J as both Navies had similar requirements in certain areas. According to my hand written notes, he also acknowledged that the F-4E benefitted from the development of the slotted stab even more as the CofG on the E had moved forward due to the fitting of the Vulcan gun and it had to retain a large tailplane area for manoeuvre at supersonic speed where the mainplane CofP has shifted aft

The notes go into a lot more detail and a lot of it concerns paperwork, which I ended up doing for six years thanks to the constant stream of modifications, upgrades (especially after the ex 892 aircraft came to Leuchars), "insisted" upon by Brough.

Never did get back to Civilisation.

DR

Thanks very much for that. A stabilizer anhedral reduction, post delivery, is plausible, which is why I weasel-worded one of my prior statements. However, even a degree of change doesn't sound like it would produce much change in area. It would reduce stabilizer thermal problems, but again my guess is that it would be by only a little. I was also surprised to read that blown flaps were deleted on the F-4M. (That may have had something to do with the unhappiness of the F-4 BLC system with the Spey bleed-air being supplied from two different compressor stages depending on the throttle setting.) However, your notes make both seem credible as a post-delivery change and lots of changes are made to airplanes after they leave the manufacturer, particularly late in their life. I can say for certain that the slotted stabilizer was developed by McAir for the F-4J and the F-4K benefited, not the other way round. See http://tailspintopics.blogspot.com/2011/09/f-4-flapstabilizer-change.html.

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On the Spey Phantom the engines were at a greater angle of incidence than on the J79 Phantom, so on the face of it there would seem to be no need to change the anhedral angle. However, the deeper engine bay would increase the side area so could a reduction in anhedral angle be used to compensate by reducing the relative vertical area of the tail plane?

Peter

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"BLC:- Blown flaps on FG1 only - cuts out at 30 degree deflection; 80% on leading edge, 20% on flaps when on; slits 0.035" over 70% of surface, 0.0015" on 30%"

DR

I am sure that when I worked on FGR2s at RAF St Athan, I took off and refitted BLC ducting from both the wings leading and trailing edges.

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I am sure that when I worked on FGR2s at RAF St Athan, I took off and refitted BLC ducting from both the wings leading and trailing edges.

Don't think so, only the FG1's had BLC. The FGR2's engines weren't BLC capable. In the early '80's the MOD looked at deleting BLC from the FG1's but I don't think it ever got past the study phase.

Duncan B

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I know that I never did a Phantom 'Q' course so I do not rightly know some things, but I did remove and fit ducting to FGR2s as I only worked on them. On start ups as part of the pre-flight checks I would feel for air along the leading and trailing edges when the flaps were lowered.

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I know that I never did a Phantom 'Q' course so I do not rightly know some things, but I did remove and fit ducting to FGR2s as I only worked on them. On start ups as part of the pre-flight checks I would feel for air along the leading and trailing edges when the flaps were lowered.

Correct, bleed air and BLC were on both the FG1 and FGR2. A Bleed Air Duct failure was a major emergency and a BLC Malfunction was significant as you had to get the speed back below 250kts so you could put the flaps down, as bleed air was still being pushed into the wing even with the flaps up.

Checking the BLC was part of the functional pre-flights as Jabba said.

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I stand corrected on the BLC. That was one of the subjects I thought I did remember from my Q course!! Must have been hung over that morning.

I have to say though that it always did cross my mind that it was a costly exercise to manufacture one mark with and one without on such a relatively small production run.

Duncan B

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Just found it in a book titled The Phantom Story by Anthony Thornborough and Peter Davies.

Reason for reduced anhedral on F-4K was to enable increased rotation with double-extending nose gear leg.

Same reference says the F-4M has standard rather than slotted stabilator - but nothing more about anhedral.

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If the US F-4s had 23 degrees and the UK Phantoms had 23 degrees and 15 minutes, then the UK birds had *more* anhedral (or negative dihedral), and thus hung lower. It's reverse logic to maintain that it was done because of the extended nose gear. That would put the tail even lower to the ground than the regular nose gear, which means that if anything you'd want *less* anhedral in the stabs.

Edited by Jennings Heilig
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  • 1 year later...

Given an approximately nine foot long stab, the stated difference of one-sixth of a degree will give about a quarter inch difference in height of the tip - which is clearance I wouldn't like to be relying on if my life depended on it.

No; this is a typo.

As for the Bucc influencing the slatted tailplane, no again; read Roy Boot's "From Spitfire to Eurofighter". He notes that MACAIR had reached a different solution to the same issue of space vs. stab authority that affected the Buccaneer when he first visited St. Louis.

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Just a little note: a quarter of a degree is not within tolerances. Aeroplanes really are built, and are maintained, to such fine values. I agree with the argument that any change due to avoiding the Spey's exhaust would have been in the direction of reducing the anhedral., but I've no idea whether they did or not. It isn't something that would have been added after delivery, as it would require modifying the structure of the mounting within the rear fuselage. If it was done, McD knew all about it.

Edited by Graham Boak
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Just a little note: a quarter of a degree is not within tolerances. Aeroplanes really are built, and are maintained, to such fine values.

Oh, yes; I've no doubt of that. What I mean is that if 1/4" is meant to provide clearance with the deck when the nose has been raised an extra 20 inches, I'd prefer to be driving the tow truck. Deck clearance is the oft-quoted, supposed reason for the supposed change.

Maybe, if they were actually trying to make the F-4K three times the price of a J, such a change might make sense.

Just checking in Roy Boot's book… he visited MACAIR in January 1965 and was told:

They added a fixed slat to the tailplane leading edge, and they were very interested to find that we had applied leading edge-edge blow to the Buccaneer tailplane to achieve the same objective.
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