Blenheim Mk IF matchup with G3M Nell or G4M Betty bombers

[Fatboy Coxy]

Hi all, I was under the impression that the Blenheim Mk IF fighter, that's the one with the four 0.303-inch machine guns in a special gun pack under the fuselage, came out poorly against the Mitsubishi G3M Nell and the G4M Betty attack bombers.

Looking at their performance stats on the Wikipedia sites, the G3M Nell had a top speed of 233 mph, the G4M Betty a top speed of 266 mph, while I can't find a speed for the Mk I, the Blenheim Mk IV also had a top speed of 266mph. These are their claimed top speeds, but I'm not sure how they would compare at the same altitudes. If operating at 20,000ft, how do they match up?

To throw a spanner in the works, the website classic warbirds, has the Blenheim Mk I with a top speed of 285mph, is that a misprint?
Bristol Blenheim | Classic Warbirds

The reason why I'm looking at this is RAF 27 squadron was equipped with these aircraft in Singapore 1941, and I was wondering how they might have faired against the Japanese bombers, putting all the other issues of the Malayan/Singapore campaign aside

Regards
Fatboy Coxy

 

[tomo pauk]

The different data sheets for the Blenheim versions among other stuff are posted here.

 

[Fatboy Coxy]

Thank you Tomo Pauk

And reading the data sheets, it confirms Warbirds claim of 285 mph top speed for the Blenheim Mk I. It doesn't give a speed for the fighter conversion, which carried the gun pack beneath the fuselage, and I would assume this would detract some speed, but not massively so.

So I'm assuming in daylight action its performance against either of the aforementioned bombers, fully laden, would be good, until they jettisoned their bombs, in which case it would struggle to close on the G4M and only gradually on the G3M.

However, operating at night, equipped with radar, it would have a clear advantage on speed, being able to close with either bomber, until it was spotted. Anything wrong with my supposition?

Regards
Fatboy Coxy

 

[buffnut453]

Thank you Tomo Pauk

And reading the data sheets, it confirms Warbirds claim of 285 mph top speed for the Blenheim Mk I. It doesn't give a speed for the fighter conversion, which carried the gun pack beneath the fuselage, and I would assume this would detract some speed, but not massively so.

So I'm assuming in daylight action its performance against either of the aforementioned bombers, fully laden, would be good, until they jettisoned their bombs, in which case it would struggle to close on the G4M and only gradually on the G3M.

However, operating at night, equipped with radar, it would have a clear advantage on speed, being able to close with either bomber, until it was spotted. Anything wrong with my supposition?

Regards
Fatboy Coxy

The only flaw in your analysis is the fact that the Blenheim MkIf airframes in Malaya were not equipped with radar.

 

[Fatboy Coxy]

Hi buffnut453, yes I think your right, but I was looking at the idea, that if the RAF had been able to provide radar for them, they would have been acceptable in that theatre at that time. That's discounting all the other problems that was going on for RAF Far East

Regards
Fatboy Coxy

 

[nuuumannn]

And reading the data sheets, it confirms Warbirds claim of 285 mph top speed for the Blenheim Mk I. It doesn't give a speed for the fighter conversion, which carried the gun pack beneath the fuselage, and I would assume this would detract some speed, but not massively so.

During official performance trials by the A&AEE at Boscombe Down a Blenheim I modified for reconnaissance achieved a maximum speed of 274 mph (TAS) at 13,000 ft and with extra effort to streamline it and an increase in boost from +5 to +9psi, the aircraft managed to reach 296 mph TAS. Interesting that during pre-war trials at Martlesham Heath, the Mk.I bomber variant managed a top speed of 280 mph, but it was noted that Avro built Blenheims exhibited lower performance than Bristol built Blenheims despite being built to the same tolerances etc. A fighter version piqued the RAF's interest after air exercises in 1937 where a bomber under interception by biplane fighters managed to evade and escape the attackers. By 1939 the Blenheim IF was in Fighter Command squadrons.

The Blenheim I Pilot's Notes don't give a maximum level speed, stating that; "For all-out level flight a maximum speed of 2,750 rpm and a boost pressure of +5 psi must not be exceeded; this speed must not be employed for a period of more than five minutes." Under the Diving Speed heading is the following: "The maximum diving speed is 285 mph ASI reading. At less than one=third throttle opening the engine speed must not exceed 2,750 rpm for periods of not more than 20 seconds with a momentary maximum speed of 3,120 rpm."

"The maximum diving speed of 285 mph ASI reading is permissible in a steady dive only."
In the section on Limiting Operational conditions, the performance listed equate to what I've written here, with no actual maximum airspeeds, except engine RPM.

I hope this helps.

 

[Fatboy Coxy]

Thank you for that nuuumannn, i appreciate your reply, qualifying her top speed. We don't have a do not exceed speed for the two Japanese bombers, which may have been greater that the speed quoted.

I still think that my supposition is good for the night fighter role with radar, she would have the speed to intercept and close. If the Japanese bomber survives the initial passing attack, she may go into a dive, and escape the Blenheim, I'm not sure they could follow using radar, very closely, although I think Japanese bombers tried to bomb in tight formations, so she may well remain in position, allowing the Blenheim to sweep by, turn, reacquire with radar and attack again.

Regards
Fatboy Coxy