Actual max speed of Blenheim I?

tomo pauk

Creator of Interesting Threads
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The data sheet notes 286 mph (dated in 1942). However, the 600+ pg book about he Blenheim notes that - after a lot of rubbing the aircraft paint, sealing and taping the joints, removal of the turret and the forward firing gun, improving the nose shape, painting with the smooth type of paint, clipping the wings - the max speed increased from 263 to 278 mph.
(the nip and tuck was initiated in order for a Blenheim to be a more fast recon bird)
Perhaps someone has some other/better data?

P1020272.JPG
 

Greyman

Tech Sergeant
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Jan 31, 2009
Bit of a repost from elsewhere:

blens22.png


Blenheim I 'special' - 11,250 lb (12,810 lb before mods)
Blenheim I - weight supposedly 10,960 lb
Blenheim IF - figure from 'The British Fighter Since 1912'
Blenheim I - 11,776 lb (+5lb sq/in)
Blenheim IV - 14,500 lb (+5lb sq/in) - boost override (+9lb sq/in)
Blenheim IV - 13,190 lb (same aircraft)

No mention of the turret's position on any of the tests. If I was forced to make a guess I'd say it was retracted.

I suspect the two blue Mk.I points are for +3.5 lb boost, which was the Mercury VIII without the boost override pulled. For +5 lb they'd be about 2 mph faster and 2,000 feet lower (lines added to sketch this out).

I have a copy of the A&AEE test of the souped-up Blenheim I (complete aerodynamic clean-up, Camotint paint, +9 boost, etc.) and the speed increase is from 274 at 13,500 to 296 at 8,100. They tested this Blenheim at various stages as they upgraded it so I assume the 278 is at some intermediate point.

EDIT: for comparison's sake the Speed-Blen made 293 at 13,500
 
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Juha3

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The official Finnish type test of Bristol built Blenheim Mk I. There were certain mods demanded by the Finns, incl. max 900 kg/1984 lbs bomb load, so it probably had the strenghtened landing gear of Mk II. No proper bombbay but bombs were carried in recesses hanging on Finnish bombracks. Max 8 x 100 kgs bombs in four long recesses under fuselage and 4 x 25 kgs bombs in small recesses in inner wings.
The attachment
Lentopaino = flight weight
korkeusmittari = altimeter
ilman lämpö = air temperature
nopeusmittari = IAS
kierrosluku = rpm vas. = left engine, oik. = right
Ahtopaine = boost
Todellinen korkeus = true altitude
Todellinen nopeus km/t = TAS km/h
 

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tomo pauk

Creator of Interesting Threads
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Apr 3, 2008
The official Finnish type test of Bristol built Blenheim Mk I. There were certain mods demanded by the Finns, incl. max 900 kg/1984 lbs bomb load, so it probably had the strenghtened landing gear of Mk II. No proper bombbay but bombs were carried in recesses hanging on Finnish bombracks. Max 8 x 100 kgs bombs in four long recesses under fuselage and 4 x 25 kgs bombs in small recesses in inner wings.
Thank you very much :)
Question: is the aircraft in question bombed up, or not? With bomb bay covered or open?
Also - was the 900 kg bomb load achieved in practice?
 
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Juha3

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Jun 20, 2019
Judging from the flight weight, the plane took off with a full crew and full tanks but without bombs and from the take-off weight the amount of fuel used for takeoff and flight to the test area has been deducted and so got the flying weight during the speed tests. The recesses were not covered. I checked and found some sorties flown with 850 kg bomb loads and IIRC have seen also 900 kg bombloads but cannot remember were they carried one of these first 18 FiAF Blenheims (BL-104 - BL-121), known as Series I. All other FiAF Blenheims had a proper bombbay with doors, Series III planes were 12 Mk IVs bought from the UK during the Winter War, Series IV were Mk Is bought from the UK during the Winter War, Series II and V were license built Mk Is by Valtion Lentokonetehdas and Series VI 10 license built Mk IVs by Valtion Lentokonetehdas. In the producing the last series Finns utilized in large scale Ikarus produced parts and semi-finished components bought via Germans.
 

Juha3

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Jun 20, 2019
A photo of a FiAF Blenheim, belonging to the Series I patch, showing the bomb recesses and eight 100 kg or 50 kg bombs in them. There are better photos but this is the best I found from the net. It is a SA photo, so a photo of the Finnish Army. http://sa-kuva.fi/neo?tem=webneo_im...b27672241640d0985344405f5de&archive=&zoom=YES

TERMS OF USE OF IMAGES
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Images may not be presented in a misleading manner or in contexts contrary to the law or good manners. For questions related to the terms of use of the images, you can contact the Finnish Defense Forces' image archive at the Military Museum.

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Juha3

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Jun 20, 2019

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