Author Topic: Typhoon speed performance (Read 2135 times)

HoHun · « **Reply #15 on:** June 06, 2005, 05:12:20 PM »

Hi Mike,

>That said, the Typhoon IB Aircraft Data Sheet 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)

mw · « **Reply #16 on:** June 06, 2005, 06:14:50 PM »

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.

HoHun · « **Reply #17 on:** June 07, 2005, 01:55:31 AM »

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)

Neil Stirling1 · « **Reply #18 on:** June 07, 2005, 11:02:38 AM »

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.

Ecliptik · « **Reply #19 on:** June 07, 2005, 11:25:25 AM »

Quote

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.

mw · « **Reply #20 on:** June 07, 2005, 12:52:09 PM »

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...

HoHun · « **Reply #21 on:** June 07, 2005, 03:04:18 PM »

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)

HoHun · « **Reply #22 on:** June 07, 2005, 03:31:01 PM »

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)

Neil Stirling1 · « **Reply #23 on:** June 08, 2005, 02:51:05 PM »

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.

HoHun · « **Reply #24 on:** June 08, 2005, 03:22:59 PM »

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)

Neil Stirling1 · « **Reply #25 on:** June 08, 2005, 03:38:53 PM »

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.