Dewoitine D.520 VS Heinkel He 112, which one has more development potential

[ThomasP]

Hey Steamed_Banana,

re (revisited)

What do you make of the chart showing the tropicalized Hurricane IIC at ~ 300 mph max speed?

FWIW The RAAF trials with their Hurricane Mk IIB(Trop) gave a Vmax of 325 mph TAS at 20,000 ft - a reduction in Vmax of around 10-15 mph and a loss of 2,000 ft in critical altitude - vs the non-tropicalized Mk IIB.

 

[Geoffrey Sinclair]

The RAAF received, after trying to decline, 1 gift Hurricane I V7476, it was the entire modern fighter defence of the country in December 1941, if serviceable.

V7476 27MU 4-9-40 Abbotsinch (crashed on del flight) 24-10-40 27MU 30-1-41 52MU 13-3-41 Australia 28-5-41

P3416 10MU 13-4-40 3Sq 24-5-40 4FPP e/f crashed in f/l in small field Dunbeath nr Wick CB 25-5-40 Sgt JJ Griffin safe R-R 30-5-40 5MU 15-7-40 5OTU 15-8-40 [DIVE TESTS] Heavy landing u/c collapsed Moreton-in-the-Marsh CB 18-12-40 F/O SB Grant safe 13MU 23-12-40 Belly landed Henlow CB 8-2-41 WgCdr RC Dawkins safe 43GDA 10MU 26-2-41 13MU 10-3-41 9FTS 15-5-41 9PAFU 1-8-42 Taylorcraft riw 25-8-43 22MU 30-9-43 Newtownards 26-11-43 Irish AC as '108'

On 25 May 1940 crashed on landing in rough field, engine failure partly due to pilot mishandling, the pilot had 4 hours on Hurricanes. Both airframe and engine classified category R = what later became category B, repairable by maintenance unit or similar. Merlin III 148212

On 18 December 1940 landed with flaps up, stalled, undercarriage collapsed. Both airframe and engine classified category R. Merlin II 173884

On 8 February 1941 defect forced a landing with undercarriage up, airframe category R, engine category A or AC. Merlin III 144935

P3856 22MU 14-6-40 7OTU 17-6-40 5OTU 13-8-40 55OTU [DIVE TESTS] Forgot to lower u/c Usworth CB 17-4-41 P/O J Jakubowski (Pol) safe 43GDA Failed to lower u/c Usworth AC 16-8-41 Sgt PC McLaughlin safe. ros 55OTU 6-9-41 Believed a/c was on fire attempted to abandon at 150ft Castletown CE 12-10-41 Sgt SJ Sculley+

On 17 April 1941 pilot error, Both airframe and engine classified category R, pilot had 2 hours on type, Merlin III 151556

On 16 August 1941, pilot error, endorsed for gross carelessness, airframe category AC, engine category R. Merlin III 151556, still had this engine when lost.

 

[Steamed_Banana]

Forgetting to lower undercarriage seems to have been a major problem for a lot of new pilots in 1940-42

 

[ThomasP]

Hey Geoffrey Sinclair,

Thank you for the info.

 

[Steamed_Banana]

Hey Steamed_Banana,

re (revisited)


FWIW The RAAF trials with their Hurricane Mk IIB(Trop) gave a Vmax of 325 mph TAS at 20,000 ft - a reduction in Vmax of around 10-15 mph and a loss of 2,000 ft in critical altitude - vs the non-tropicalized Mk IIB.

That's interesting and certainly plausible, but I think that chart I posted is real too, it came from a discussion on here and was posted by someone with great deal of Hurricane knowledge, I just don't know the source. If I have time I'll try to track it down.

 

[ThomasP]

The chart is real, but the question is who generated it and what tests or other sources were used..

Somethings that should be understood are:

1. Between the test reports from "WWII Aircraft Performance" (which I think is where the chart you posted is from originally) and bits and pieces from other websites and individuals, we currently have digital access to less than 1% of the tests performed by A&AEE/RAE, AFDU, and operational squadrons, involving the aircraft that the UK & Commonwealth operated in WWII.

2. As I mentioned up-thread, the results from the official tests do not necessarily give the maximum performance for the average aircraft type being tested - only the individual aircraft in the test.

3. The values for Vmax & ROCmax in the tests are dependent on the specific weights, drag inducing components, engine output (ie is the engine up to snuff or not), etc, among other factors. Sometimes the document mentions if the results are corrected to a certain weight or condition of wear, and if they should/should not be considered representative of the average operational airframe, and sometimes they do not indicate such things.

4. The chart you posted gives the Vmax for 1 airframe type under x condition, but there were multiple tests performed by A&AEE/RAE, AFDU, operational squadrons, etc, for the types.

One example of why I will say do not concentrate too tightly on the chart values is the speed for the Hurricane Mk IIC on the chart you posted. The source of the data for the chart is listed as "RAF Fighters Part 2" which is from a series of books - not an official original source document. Plus, as already noted up-thread, there is the 339 mph TAS listed on the ADS (which is an original source document) at mean weight.

Also, note that at the top of the chart it has a note 'Hurricane speed using Mustang Merlin XX +12 lbs from "Rolls Royce and the Mustang', which is another book and not an official original source document from test results. Plus why was this statement even posted, and why was an original source document not used - the Merlin XX power vs altitude curves from Rolls Royce have been available at least since 1998, which is when I first downloaded them.

Also, note the entry for the 'Hurricane IIA SL[?] II +12 lbs as of 16/3/2004' and 'HurricaneIIC +12 lbs data RAF Fighters Part 2 pg 22 30/12/2014' and 'Hurricane IIC Trop +12 lbs as above 30/12/2014'. How do the dates "16/3/2004", "30/12/12", and "30/12/2014" relate to the subject under discussion - the chart was obviously put together during or after the years 2004 thru 2014, and given that the sources of the data are books and not original source documents . . . ???


FWIW, the Hurricane Mk IIB(Trop) Vmax of 325 mph TAS at 20,000 ft is from my notes (so from a secondary source since I did not mark it otherwise) and my notes state "451 Sqn undertook operational testing of one of their first(?) Hurricane Mk IIB(Trop) during late-42 while in the Middle East". 451 Sqn was an RAAF squadron that served in the MTO and NA theaters.

Since the 451 Sqn tests were performed in the field a trailing pitot sensor would not have been used, and they would have to have relied on the pressure altitude and ASI recorded, with the speed correction values as listed in their Pilot's Notes, with the correct TAS calculated.

Also FWIW, based on the drag factors I have available, and the engine outputs (with and without RAM), the math works out pretty close.

 

[Steamed_Banana]

I think the Devil is indeed in the details, and I suspect if a Hurricane is slowed down quite that much would be due specifically to the Vokes filter and possibly some other fittings like bomb shackles, external BP windscreen, RDF loop etc.

Maybe the dates mentioned on the chart refer to when the data was retrieved but I don't know . I was hoping someone here would recognize Neil Sterling but I guess not. WWII Aircraft Performance seems to have a lot of broken links in the past few months, but maybe I'll try poking around on there for the data. I seem to remember some kind of Australian test with somewhat similar findings but that could be wrong.

Good point about the small percentage of documents currently available online. WWII Aircraft Performance has been a huge help for me in understanding period aviation. What do we need to do to find more records? Are these sitting in old archives just not yet scanned or are they lost or what? There are certainly many gaps especially for such as Italian and Japanese, French, Soviet etc. aircraft that I'd love to see more about, and also with some of the US and British types as you say.

 

[Steamed_Banana]

Ah, I just checked, and that chart is right there in the section on the Hurricane on WWIIaircraftperformance.org, so i would guess it is legit and Neil Sterling seems to be linked to the site, which is run by some people here right?

https://www.wwiiaircraftperformance.org/hurricane/Hurricane-II_12lbs.jpg

Hurricane Mk II Performance

Hurricane Performance Testing, wartime flight trials and reports of Hurricane aircraft. Hurricane Mk I data.

www.wwiiaircraftperformance.org

They also show this chart for IIB at +9 boost

all in all the Hurricane section seems a bit sparse compared to the entries for some of the other types, and I don't see any reports about tropicalized Hurris or use with the Vokes filter.

Several of the other pages are throwing a 404 error

 

[gruad]

Which He 112 (wing shrank considerably from the early prototypes to production B models) and which late Spitfires?
MK V or MK VIIIs or Griffon powered?

There is a lot of hidden stuff that is hard to figure out. Like actual airframe strength and what is needed to change it.
Difficulty in changing/enlarging the cooling systems.
Changing centers of gravity.

A major Spitfire advantage is that starts out with a wing about 32% bigger so it can handle increases in weight somewhat better without low speed handling going in the toilet.

You can stick a bigger wing on the D. 520 and stick a 20mm in each wing when the new, larger engine takes up the space for engine mounted gun but if you change enough stuff do you really have a D.520 anymore?
View attachment 887163
Might want to move the cockpit around 1 meter further forward so there is some chance of doing deflection shooting.

Looks like one of the cars out of Whacky Races!

 

[Steamed_Banana]

If they make a Patreon or something for WWIIaircraftperformance I'll definitely chip in, by the way. just for the record. I'd bet a lot of people would.

 

[ThomasP]

Hey Steamed_Banana,

re

They also show this chart for IIB at +9 boost

Note that in the header of the above chart it says " 'M' BLOWER ".

The Merlin XX was the RM3SM model - with the M indicating Moderately supercharged - it is the lower gear of the 2-speed supercharger.

In lower gear, the up-to-snuff Merlin XX/21/22/23/24/25/28 were rated at 1240 -1260 BHP at 3000 rpm with +9 lbs boost at ~11,000 - 12,000 ft critical altitude when static - with the aircraft critical altitude increasing to 13,000 - 14,000 ft at ~300 - 320 mph TAS with RAM.

In high gear (the S in RM3SM) the Merlin XX/21/22/23/24/25/28 were rated at 1140 - 1175 BHP at 3000 rpm with +9 lbs boost at 18,250 - 18,500 ft when static - with the aircraft critical altitude increasing to 20,000 - 22,000 ft at 320 - 340 mph TAS with RAM.

Here is the tabulated data for the graph you posted above for Hurricane Mk IIB Z2346. It shows the Vmax during the test in low gear is 305 mph TAS at 3000 rpm at +9 lbs boost at 13,000 ft, and 330 mph TAS at 3000 rpm at +8.8 lbs boost at 20,800 ft. However, it should be noted that both the boost and the altitude with RAM in high gear are lower than they would be if the engine was up-to-snuff.

The above table was given to me on a flash drive (along with a lot of other files) by a friend who died a couple of years ago. I still have not gone through all of them and do not know where he acquired most of them were. Many of them are dated from the early-2000s.

 

[ThomasP]

re

I was hoping someone here would recognize Neil Sterling but I guess not.

Most of the regulars on this forum are familiar with Neil Stirling. He has been a member of the forum for some time, and has posted under a couple variations of his name since 2012, although I do not think he has posted recently.

 

[GregP]

Most of us know Neil Sterling. 've known about him for decades, and I'm not unusual in any particular way ... aside from being ... old.