Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Flyboy on May 29, 2005, 10:58:51 AM
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I started THIS THREAD (http://www.hitechcreations.com/forums/showthread.php?s=&threadid=151876) in the general forum. i think it should be here tho.
here are some figures to play around with.
in AH on the deck, fuel burn set to 0.0000000 (no burn at all)
the bolded number indicates WEP
typhoon at 25% fuel: 372 / 357
P51d at 25% fuel: 368 / 355
typhoon at 100% fuel: 371 / 356
P51d at 100% fuel: 366 / 354
the thing that stand out the most is the fuel load barely make any difference in speed.
anyone care to explain why? or is it a bug?
then i found the following Flight test (http://home.epix.net/~cap14/typhoon.html)
now im No expert, but clearly there is something very wrong in either AH or the test they performed.
Here are the contradictions i found between the report and AH tiffi.
- deck speed is wrong, AH tiffi is faster at 357 compared to 345.5.
- according to the source the overall top speed of the tiffi (whats the correct technical name?) is at 20,200feet and is 394.5Mph. AH tiffi does 400MPH.
- AH tiffi fail to hold a boost of +7 at 20,200.
- the source states
-------------------------- R.P.M. Boost lb/sq.in.
Maximum permissible for climb 3500 +6
Maximum permissible for level flight (5 min. limit) 3700 +7
AH tiffi can hold +7 boost for unlimited amount of time.
Another thing i dont understand about the reort is when did they engage the 2nd phase of the SC.
in the climb chart it shows 12,600feet but on the speed chart it shows 15,000feet.
lastly, the report figures are quite low, anyone have a different performance figures?
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ow im No expert, but clearly there is something very wrong in either AH or the test they performed.
Here are the contradictions i found between the report and AH tiffi.
- deck speed is wrong, AH tiffi is faster at 357 compared to 345.5.
That test is for a very early Typhoon.
It ran at 7 lbs boost with a 3 bladed prop. The AH Typhoon is a later version with a 4 bladed prop (iirc) and running at 9 lbs boost, which provides a lot more horsepower.
- AH tiffi fail to hold a boost of +7 at 20,200.
What boost does it hold?
AH tiffi can hold +7 boost for unlimited amount of time.
The Typhoon with the Sabre IIa engine had a 1 hour limitation of 7 lbs, which is, to all intents and purposes, unlimited.
Another thing i dont understand about the reort is when did they engage the 2nd phase of the SC.
in the climb chart it shows 12,600feet but on the speed chart it shows 15,000feet.
Ram air effect. The faster you go, the more air builds up in the intake, increasing effective air pressure. So at high speed you can maintain a higher boost level at a particular altitude than at low speed.
lastly, the report figures are quite low, anyone have a different performance figures?
Well, that's an early Typhoon, 3700 rpm 7 lbs boost. The Sabre IIa allowed 3700 rpm, 9 lbs boost, the Sabre IIb 3850 rpm, 11 lbs boost (and possibly as much as 13 lbs). Don't know how many Typhoons recevied the Sabre IIb though.
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Did a little more research -
The Sabre IIA was fitted to the first 105 Tiffys only, after that the Sabre IIB then the IIC became standard. Guessing ours is the IIB or IIC. More likely IIB as over 3000 Tiffys were made.
Tail probs - Initial 'fix' was started in 1942 by adding a row of strengthening fishplates round the rear fuselage.
Later on a Tempest tail was fitted (we dont have that)
Prop - According to the Air Ministries own documents this did little more than reduce the take-off run by 150 to 200ft. Fitted in 1944.
So it begs the question - How many 4 bladed, Napier IIB Tiffies were around in 1944, or had most been upgraded to the Sabre IIC?
Could it be we not only have a dog Spit 9, but a dog Tiffy also? If so we have a 1942 Tiff with a 4 bladed prop.
Still hard to find 'official' performance graphs.
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I've no idea of the number of typhoon with 4 blades propeller.
(http://www.onpoi.net/ah/pics/users/33_1117988286_t1.jpg)
(http://www.onpoi.net/ah/pics/users/33_1117988317_t2.jpg)
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internal weight (gas load) will not affect the top speed of a plane.
It will affect the acceleration, the time it takes to GET to that top speed, but you will arrive at the same top speed.
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Originally posted by straffo
I've no idea of the number of typhoon with 4 blades propeller.
(http://www.onpoi.net/ah/pics/users/33_1117988286_t1.jpg)
(http://www.onpoi.net/ah/pics/users/33_1117988317_t2.jpg)
Wierd that goes against what I read saying only the 1st 150 Tiffs off the produciton line had Sabre IIA's.
In fact it looks very suspicious, theres no mention at all of the Sabre IIC fitted to later aircraft.
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Source is : Hawker Typhoon Tempest and Sea Fury by Kev Darling.
I'm still tring to find a book by Christopher Shores suposed to be more accurate.
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Originally posted by straffo
Source is : Hawker Typhoon Tempest and Sea Fury by Kev Darling.
I'm still tring to find a book by Christopher Shores suposed to be more accurate.
Kev Darling, Lol thats OK Straffo Sweetie.
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:lol didn't noticed the author name :D
As I've it in front of me ISBN : 1 86126 620-0
If you are a 2TAF fan I urge you to get :
2nd Tactical Air Force Volume One "Spartan to Normandie" by Christopher Shore and Chris Thomas
ISBN :1 903223 40-7
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If you want Typhoon (and Tempest) production numbers read:
The Typhoon and Tempest Story
Thomas & Shores
ISBN 0-85368-878-8
The Hawker Typhoon & Tempest
Mason
ISBN 0-946627-19-3
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Kev, where did you find that the Tempest tail was fitted?
The majority of the 4th production run (5-4-43 > 7-12-43) of 600 serialed JP and JR had there IIAs replaced by IIBs.
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Originally posted by MiloMorai
If you want Typhoon (and Tempest) production numbers read:
The Typhoon and Tempest Story
Thomas & Shores
ISBN 0-85368-878-8
The Hawker Typhoon & Tempest
Mason
ISBN 0-946627-19-3
.............
Kev, where did you find that the Tempest tail was fitted?
The majority of the 4th production run (5-4-43 > 7-12-43) of 600 serialed JP and JR had there IIAs replaced by IIBs.
Sorry, I should have been more specific, my bad -
They found the problem with shedding tails was caused by vibration.
Qucik 'fix' was to strengthen the area with fishplates, later on they fitted a Tempest type tailplane that cured the problem.
When was the Sabre IIC used?
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Kev, you do know that the fin of the Tempest was just a filleted Typhoon fin. AFAIK the slightly increased sized stab and elevator was not fitted to the Typhoon.
The fishplates added hardly any strength and was more for reassurance of the pilots. The tail failures were due to fatigue failure of the elevator mass balance mounting bracket. (see pg 40-42 of the Mason book for more detail)
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Emm:
"internal weight (gas load) will not affect the top speed of a plane.
It will affect the acceleration, the time it takes to GET to that top speed, but you will arrive at the same top speed."
Not exactly. Adding weight adds induced drag. But on that kind of a plane it does not make very much of a difference.
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Originally posted by MiloMorai
Kev, you do know that the fin of the Tempest was just a filleted Typhoon fin. AFAIK the slightly increased sized stab and elevator was not fitted to the Typhoon.
The fishplates added hardly any strength and was more for reassurance of the pilots. The tail failures were due to fatigue failure of the elevator mass balance mounting bracket. (see pg 40-42 of the Mason book for more detail)
According to the Air Ministries own records the increased sized stab and elevator were fitted.
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Neil Stirling & I have been working on Typhoon Performance. We’ve not sorted it all out yet, but here’s a start:
Typhoon Performance (http://www.spitfireperformance.com/typhoon/typhoontest.html)
(http://www.spitfireperformance.com/typhoon/typhoon-level-ft-jpg)
The tests are not perfect – they hardly ever are. R.7700 had extended exhaust stubs (for CO contamination tests) With respect to R.8762 it was noted that: “This aircraft has been on test work for a considerable time, and the external finish of the aircraft has deteriorated during this period. The results should not therefore be regarded as typical for new production aircraft. This deterioration will not, however, invalidate the comparison between the results at combat and old all-out level rating.”
That said, the Typhoon IB Aircraft Data Sheet (http://www.spitfireperformance.com/typhoon/typhoon-ads.jpg) gives performance with 9 lbs/3700 RPM as 374 mph at 5,500 ft and 405 mph at 18,000 ft. These figures correspond reasonably well with R.8762 at +9 lbs when the condition of R.8762 and its lower FS gear height are taken into account.
Comparing to AH:
(http://www.spitfireperformance.com/typhoon/ typhoonspeed-ah.gif)
The FTHs seem to suggest +9 lb boost, the speeds suggest +11 lbs boost. Bit of a puzzle really... Could be +11 lbs (Sabre IIB), but I don’t think the FTH’s match that.
Edit: To hopefully clarify; the only logical conclusion I can make with respect to AH is that the black line in the AH chart is +9 lbs, and the red line (emergency) is +11 lbs.
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Hi Mike,
>That said, the Typhoon IB Aircraft Data Sheet (http://www.spitfireperformance.com/typhoon/typhoon-ads.jpg) gives performance with 9 lbs/3700 RPM as 374 mph at 5,500 ft and 405 mph at 18,000 ft. These figures correspond reasonably well with R.8762 at +9 lbs when the condition of R.8762 and its lower FS gear height are taken into account.
I ran it through my calculator and arrived at 376 mph @ 5250 ft and 400 mph @ 17400 ft for +9 lbs/sqin, based on the drag of R7700.
(I'm working from a Sabre power chart with 400 mph ram that must be for equivalent shaft power, and I'm using the 3-bladed propeller, too, so I'm considering that a good fit :-)
I'd say RB329 would be faster than R7700 on the same boost - could this be due to the propeller? Do you have the diameter of the 4-bladed propeller? I'd assume it would be a question of efficiency and not the diameter, unless the Sabre IIA also changed the reduction gear ratio. (I'm using 0.274.)
>The FTHs seem to suggest +9 lb boost, the speeds suggest +11 lbs boost. Bit of a puzzle really... Could be +11 lbs (Sabre IIB), but I don’t think the FTH’s match that.
Hm, the heights seem to be low indeed, at least for low gear. Note that the difference between red and black is also greater in low gear than in high gear. Could it be that it's +11 lbs/sqin in low gear and +9 lbs/sqin in high gear? Looking at my spreadsheet, I seem to have tried a similar combination for my Tempest analysis a while back ... unfortunately, I can't remember what gave me the idea.
(Low gear full throttle height of course seems high for +9 lbs/sqin already, it would be an even poorer match for +11 lbs/sqin of course.)
Regards,
Henning (HoHun)
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Hi HoHun:
>I ran it through my calculator and arrived at 376 mph @ 5250 ft and 400 mph @ 17400 ft for +9 lbs/sqin, based on the drag of R7700.
>(I'm working from a Sabre power chart with 400 mph ram that must be for equivalent shaft power, and I'm using the 3-bladed propeller, too, so I'm considering that a good fit :-)
Indeed, I'd agree that's a good fit - nice work :)
>I'd say RB329 would be faster than R7700 on the same boost - could this be due to the propeller? Do you have the diameter of the 4-bladed propeller? I'd assume it would be a question of efficiency and not the diameter, unless the Sabre IIA also changed the reduction gear ratio. (I'm using 0.274.)
I'll check on the prop and red. gear when I have the chance. As Kev367th stated, however, the 4 blade prop primarily helped with take-off, especially when loaded with ordinance. My sense is that R.7700 is a tad draggy, R.8762 is draggier still and RB.329 is just real clean :)
With regards to AH full throttle heights: perhaps Doug is figuring 3850 RPM? Dunno, beats me.
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Hi Mike,
>With regards to AH full throttle heights: perhaps Doug is figuring 3850 RPM?
Hm, could be, not sure how to figure the gain in full throttle height though. Maybe Greg's engine calculation can help here?
Complex situation in any case. 3850 rpm would appear to be a Sabre IIB, but the Sabre IIA could also run +11 lbs/sqin boost according to the engine chart I found.
"Sabre IIA engines have strengthened propeller shafts permitting +11 lb/sq.in. boost with 150 grade fuel."
Interestingly, the M gear power graph is provided in two variants, for +9 lbs/sqin and +11 lbs/sqin, while the S gear only features +11 lbs/sqin.
I'm not sure what that means - perhaps in S gear, 150 grade and +11 lbs/sqin could be used with the Sabre II without the strengthened propeller shaft since the shaft didn't have to transfer as much power in S gear anyway.
However, the Typhoon IA/IB Pilot's Notes permit only the following parameters:
Sabre II: +7 lbs/sqin @ 3700 rpm (5 min), +6 lbs/sqin @ 3500 rpm (60 min)
Sabre IIA: +9 lbs/sqin @ 3700 rpm (5 min), +7 lbs/sqin @ 3700 rpm (60 min)
(That's AP1804A, second edition, dated November 1943, with the first amendment from July 1944 incorporated. The amendment didn't change the engine settings, though. I'm not quite sure about the naming conventions - theoretically, the first edition might have had different content, or AP1804 (without "A") might have differed, too. If you know how the RAF handled Pilot's Notes updates, I'd be very interested :-)
Comparing the engine chart to the November 1943/July 1944 settings, I'd suspect that the +11 lbs/sqin settings were reserved for the V-1 chasers, at least at first. From Clostermann's books, I'd conclude that 150 grade fuel was made available to fighter units in Europe, too, but I haven't gone back to check the date. (He was flying Tempest not Typhoon, but still ...)
Regards,
Henning (HoHun)
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Hi guys,
4 blade prop 14ft dia, The Typhoon and Tempest Story, Thomas and Shores.
Sabre IIA reduction gear ratio, .2742 to 1, British Piston Aero Engines And Their Aircraft, Lumsden. Sabre VII the same, Napier document.
Typhoons fitted with Sabre IIb, The Hawker Typhoon and Tempest, Mason.
Fourth production batch 600 aircraft, initially fitted with Sabre IIa, many refitted with the Sabre IIb in 1944.
Fifth batch 800 aircraft, described as Sabre II.
Sixth batch of 400 aircraft, final few fitted with the Sabre IIb. 15-6-44 to 5-1-45
Seventh batch 300 aircraft Sabre IIb 5-1-45 to 13-11-45.
Performance Sabre IIb and 4 blade prop, Aircraft of the RAF since 1918, Thetford.
412mph at 19,000ft.
Back to the Hawker Typhoon and Tempest by Mason on page 89 it is stated that RB 306 underwent a rigorous performance check at Langley in Nov 44, a speed of 422mph at 12,800ft M.S was obtained. This doesnt sound right 12,800ft is much to high for M.S, alternatively it could be FS although the Sabre would have to be running at about +13lbs or more?
Neil.
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Originally posted by Krusty
internal weight (gas load) will not affect the top speed of a plane.
It will affect the acceleration, the time it takes to GET to that top speed, but you will arrive at the same top speed.
Is this true?
Wouldn't increased weight increase the lift neccessary to maintain level flight? Since wing area does not increase this means a greater positive AoA for level flight and thus a lower achievable speed. This is induced drag I think. Perhaps the effect is minor but I don't believe that weight has NO effect on top speed.
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Hi HoHun:
That sound about right to me :) I have the 2nd edition (Nov 43) of the Typhoon Pilots Notes where in it gives the limits as +9 lbs, 3,700 RPM when equipped with Sabre IIA. Same as yours with the amendments I gather. My Tempest Pilot's Notes from July 44 also gives +9 lbs, 3,700 RPM with the stipulation: "Figures in brackets apply to engines embodying Mod. Sabre 158 or 297 and Mod. Sabre 276." We know that Mod. 158 or 207 were for a strengthened propeller reduction gear assembly. We also know that those Sabre IIA's having Mod. No. Sabre/158 or 297 were easily converted to Sabre IIB's (+11 lbs/3,850 RPM) by the incorporation of a new boost control cam (Mod. No. Sabre/433) and a new boost control capsule (Mod. No. Sabre/435). Looks like Neil is already working the Sabre IIB story further :) We'll keep digging, but it looks to me, from what we know now, that the Sabre IIB became the standard engine for both Typhoon and Tempest somewhere around late 44/early 45. That seems to me to be what Doug modeled in AH (I'll not nit-pick it any further).
One thing is nagging me - on the face of it, I would think that changing from a three blade to a four blade propeller would have a greater effect than generally stated. Now, there are comments about reduced vibration and a need for a larger horizontal stabilizer. Might there not also have been some effect on acceleration, dive speed, FTH, stall even? Hmm, just wondering aloud...
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Hi Ecliptic,
>>internal weight (gas load) will not affect the top speed of a plane.
>Is this true?
Only as an approximation as long as you're talking about small angles of attack.
At negative angles of attack, such as achieved at top speed, the reduced fuselage drag at a higher angle of attack might actually outweigh the increased induced drag of a heavier aircraft (I reckon :-)
Regards,
Henning (HoHun)
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Hi Neil,
>4 blade prop 14ft dia, The Typhoon and Tempest Story, Thomas and Shores.
Thanks! That's the same value I've found for the three-bladed propeller. (My model makes no difference for the number of blades, only for the tip speed.)
The Typhoon seems unusual in combining a very large propeller with very low tip speeds thanks to a very conservative gearing, keeping Mach-induced efficiency losses to a minimum.
(I don't know whether they paid a price in efficiency elsewhere, or if they simply had a superior propeller :-)
>Fourth production batch 600 aircraft, initially fitted with Sabre IIa, many refitted with the Sabre IIb in 1944.
Hm, where these production batches finished chronologically? They don't seem very coherent with regard to the engine fit.
>Back to the Hawker Typhoon and Tempest by Mason on page 89 it is stated that RB 306 underwent a rigorous performance check at Langley in Nov 44, a speed of 422mph at 12,800ft M.S was obtained. This doesnt sound right 12,800ft is much to high for M.S, alternatively it could be FS although the Sabre would have to be running at about +13lbs or more?
I think +13 lbs/sqin is spot-on! I get 410 mph @ 12800 ft for R7700, and it would be more for RB329.
I guess that must be one of the engine-consuming settings Eric Brown talked about :-)
Does "Langley" refer to a US testing location? What's the story behind this?
Regards,
Henning (HoHun)
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Hello HoHun,
Hm, where these production batches finished chronologically? They don't seem very coherent with regard to the engine fit.
I think you are refering to batch 5, this was delivered between 8-12-43 and 15-6-44. My information is the IIa became standard from mid 43. I can only speculate as to why Mason wrote this, perhaps there was a large mix of engine types.
I think +13 lbs/sqin is spot-on! I get 410 mph @ 12800 ft for R7700, and it would be more for RB329.
Thanks that helps!
Does "Langley" refer to a US testing location?
No, Langley Buckinghamshire is where Hawkers factory was located.
Thanks for your help.
Neil.
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Hi again,
>I think +13 lbs/sqin is spot-on! I get 410 mph @ 12800 ft for R7700, and it would be more for RB329.
Could RB 306 have been upgraded to a Sabre V engine? +13 lbs according to my estimate would result in about 2600 HP, which is the reported power output for this engine variant.
>I guess that must be one of the engine-consuming settings Eric Brown talked about :-)
I've looked it up, and Eric Brown tested the Tempest at up to 10.25 lbs/sqin. (Maybe +11 lbs/sqin was the goal, and the boost regulator had some variance.) This seems to fit the Tempest V/Mustang III/Spitfire XIV speed comparison chart repeatedly posted where the Tempest V with Sabre IIA is listed with +11 lbs/sqin @ 3700 rpm.
The engine failure Brown had with the Tempest came after 3.5 min at +8.5 lbs/sqin at 7000 ft. (That was the maximum attainable boost.) So maybe I overestimated the role boost plays in wrecking engines ;-)
Regards,
Henning (HoHun)
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Hi,
Could RB 306 have been upgraded to a Sabre V engine? +13 lbs according to my estimate would result in about 2600 HP, which is the reported power output for this engine variant.
Luckily Masons book contains a summary of flight test development work.
RB 306 is listed as of November 44 as having a Sabre IIa and a 4 blade prop, it was flown on speed trials with various under wing loads.
The Sabres boost history gets very murkey +7 +9 and +11lbs for definate, higher boost recorded but no official confirmation.
Neil.