Practical/reliable max. speed of Ki-27?

[GuerraCivil]

During the years I as well as others have learned to be skeptical on technical details of aircraft represented in books and web sources.

One example is Ki-27 "Nate" - some sources refer that the max. speed of the plane was as much as 460 - 470 km/h at the altitude of 3500 - 6000 meters, at 2000 meters 440 km/h and at sea level 420 km/h.

I´m a bit skeptical on these numbers. From Soviet test flight results with a captured Ki-27 I have read that it did make up to 400 km/h at sea level (I do not know speed results of Soviet test flights at altitudes, but presumambly the max. speed was lower than the supposed 460 - 470 km/h at 3500 - 6000 meters).

Also from one Japanese combat report I have read that Ki-27 had difficulty to catch Blenheim Mk IV bombers over Burma (and it was not easy to escort their own Ki-21 bombers due to the speed of the latter).

As Blenheim Mk IV made it at maximum about 430 km/h at 3500 - 4000 meters and was difficult catch for "Nate", I find it difficult to believe that Ki-27 would have been as fast as 460 - 470 km/h at the same altitude. Perhaps the max. speed was at best about 420 - 430 km/h at 3000 - 5000 meters? To catch the Blenheim the Ki-27 had to dive on it.

One thing to be considered: to my understanding Japanese pilots (and Thai pilots) flew Ki-27 almost always with opened cockpit or had the sliding part of canopy removed to improve visibility. This probably had also some slowing effect to the speed of the plane?

[drgondog]

Absent knowledge of the condition of the airframe, the loading during the trial runs - how could anyone answer the question. Another question - Ki 27a or Ki 27b with the 710hp Ha1b engine which had 10% more horsepower

[GuerraCivil]

I guess that the estimated max. speed of 460-470 km/h at the altitude of 3500-6000 meters refers to brandnew Ki-27b (Otsu) without full load. And most likely a very optimistic prototype figure without ammo load, not having full fuel load, paint etc. A comparison could be made with Curtiss P-36/Hawk 75 which practically never made it up to overoptimistic Curtiss factory figure 500 km/h which is often referred (without criticism) in English/American literature. More of this at another forum: http://forum.warthunder.com/index.ph...6#entry3817707

The combat records of Ki-27 pilots over Burma in the spring of 1942 state that they had difficulty to catch Blenheim Mk IV (according to one Japanese pilot it was actually faster than their "Type 97"). My rough guess is that the well-used airframe (the Ki-27 were already quite old planes in 1942) with combat load could not be more than 420 km/h at its optimal altitude (probably 4000 - 6000 meters).

I have read that AVG pilots made extensive tests with one captured and intact Ki-27 Otsu in the spring 1942 but I do not know if their test results have been written down and published anywhere. Also Claire Chennault testflew one Ki-27 and supposedly wrote a report of its performance for the US military intelligence.

[Juha]

RAF info, Blenheim Mk. IV max 275mph (443km/h) at 13,800ft, and British max speeds are usually with loaded plane, some 95% of MTOW IIRC, with +9lb boost 251mph (404km/h) at 1,000ft and 254.5mph (410km/h) at 2,000ft. So at low down difficult to catch for Ki-27 even when loaded with bombs, without bombs even more difficult. Of course the type of the undernose turret or lack of it had an effect on the max speed, a brief look on Warner's Blenheim book showed planes without the undernose turret and with the more angular one. Dimitar Nedialkov in his In the Skies of Nomonhan gives for Ki-27 max speed of 468 km/h at 3,200m, 395 km/h at sl. The old Green's and Swanborough's Japanese Army Fighters Part 2 gives for Ki.27-Otsu 427 km/h at 1 000 m, 445 km/h at 2 000 m, 462 km/h at 3 000 m, 470 km/h at 3 500 m, 469 km/h at 4 000 m and 468 km/h at 5 000 m.

[Graham Boak]

You will need to knock a few mph/kph off the top speed of a tropicalized Blenheim, because of the additional filters and intakes. The hot weather would presumably apply equally to both aircraft's estimates. I also suspect that the top speed of the Blenheim is quoted with dorsal turret retracted.

[Juha]

Originally Posted by Graham Boak

... I also suspect that the top speed of the Blenheim is quoted with dorsal turret retracted.

Maybe or at least without the undernose turret or with the rather useless teardrop-like perspex undernose turret. I forgot to mention that the specs I gave for Mk IV were from the BoB era.