Tuesday, September 22, 2015

Workmanship of Axis aircraft

In Richard M. Bueschel's series on Japanese WWII fighters (i.e, "Nakajima Ki-84 Hayate in Japanese Army Air Force Service) and Rene Francillon's "Japanese Aircraft of the Pacific War"), the authors repeatedly mention that the latter-day Japanese fighters, while technically equal to their Allied counterparts, were plagued by variable and poor workmanship; Bueschel writes that the Ki-84 could only rarely achieve a level speed of 400 km per hour. For example, the level speed of the Nakajima Ki-84 fighter was rated at 620 km per hour, yet reportedly most late-production specimens could not achieve even 400 km per hour due to poor workmanship of the airframe and engine.

As for the Ki-84, I remember talking to a P-51 pilot from SWPA. He said that sometimes they would try to intercept the Franks, which could and did show them a clean set of heals. If this was an overall problem I think this "legging it" would not have happened. A good question would be where did this information come from. Was it from the US, who did and still do put down aircraft that were either superior or at least on par with their own, or was this actual Japanese records showing this.

I apologize to our American Friends out there, the above comment is not an attack on you guys but just something that I have seen and heard over the
years, by various Authors and Vets.

I recall reading accounts of trials of captured Japanese aircraft, in particular the Ki-84, which stated that the fitting of US spark plugs made a vast difference to the aircraft's performance. The fitting of US brake pads too, where possible was found to be a must too! Material shortages and quality problems in seemingly minor areas can have a dramatic effect on overall performance. 

Were the late war Luftwaffe fighters subject to similar inconsistencies in workmanship and quality control?

Its an accepted fact that workmanship on the production Me-262s could vary by a huge margin. With components from several sources and locations, it was impossible to get the same kind of tight tolerances that a single factory of that period could produce. There were reports of some Me-262s that were discovered to have foreign objects (tools, supplies, etc.) pushed into void spaces by their builders, no doubt in response to their slavery. Also, I read here once that a Junkers 290 crashed and it was later determined that the tail section was delivered with a very large amount of very heavy tools hidden in the tail.

The Swiss thought the 109Gs they received were terrible, as opposed to the few Fs that they received mid-war. The French thought the same about the Fw.190s they tried to operate postwar. This was partly due to wartime pressures, and partly to the influence of all the foreign (slave, if you like) workers employed in the German industry late war.

It should be added that late P-40s were much cruder than the early-war aircraft, though this is due to an intense "simplify and add more lightness" campaign rather than a decline in workmanship as such.

Bf 109 quality as perceived in Finland

The Finnish AF also observed a big decline in workmanship quality of Bf 109G-6s received in summer 1944, compared with quality of G-2s received in winter-spring 1943. All received 109s were therefore thoroughly overhauled at VL (except a few aircraft which were ferried directly to the frontline, and performed the first missions still with German transfer insignias/see Vol 6 of FAF History by Keskinen&Stenman). The FAF and VL tried very hard to negotiate a full reparation license for the 109 (including drawings, spares and tools) for the 109, but for obvious political reasons the Germans were very reluctant (it was known to the Germans that contacts had already been taken to Moscow in April 1943). Complete sets of drawings and tools for the 109 were never delivered, why VL tried to design the indigenous Pyƶrre-Myrsky around the Daimler-Benz 605 engine,

Flight characteristics

Messerschmitt Bf 109 undergoing wind tunnel testing in 1940.

Flight characteristics - Climb and Ceiling

1."climb rate"
This defines the maximal vertical speed of an aircraft when climbing, while *retaining airspeed*. So no drop in airspeed is permitted for max. climb rate. Climb rate is usually defined in feet/minute

2. "initial climb"
Same as for climb rate, but only for the situation directly after take-off. This figure is important when trees or other high objects are in the direct vicinity of the runway. Aircraft should have a vertical clearance of 15m (45 feet) to any nearby object. So if an aircraft has a poor initial climb, the area adjacent to the runway should be clear of tall objects.

3. "Ceiling"
Ceiling = maximum height (usually measured in feet).
There are two ceilings actually. The operational ceiling (which is the one you probably refer to) and the aerodynamic ceiling.
The first defines how high an aircraft can fly 'normally', thus no drop in airspeed, and reasonable figures like stall speed.
This is where we get to the aerodynamic ceiling. At a certain altitude the aircraft is limited in the 'allowable' speeds. The margin between stall speed and maximum attainable airspeed narrows down to 0 at the so-called 'death man's corner'. A Lockheed U-2 spyplane has an airspeed margin of 30 kts at it's operational height, which is a very narrow margin!

4. "Service Ceiling"
The ceiling at which an aircraft can be flown operationally, which is economically sound or prescribed by the aircraft's mission. As stated, this service ceiling is ridiculously high for the U-2, with little margin for mistakes.

In American usage, "service ceiling" is the altitude at which an aircraft's rate of climb falls to 100 feet per minute. I just skimmed an English book in which they claimed that "service ceiling" was the altitude at which the rate of climb fell to 500 feet per minute. Considering that most WW2 aircraft, other than fighters, have INITIAL rates of climb around 500-700 feet per minute, this would seem a rather harsh standard. Maximum ceiling is worthless for comparisons.

Many German rates of climb are given in meters per second, which I believe is what is displayed on rate of climb indicator gauges (at least modern ones). Comparing an aircraft rated at "22 m/sec" against an aircraft rated at "5.6 minutes to climb to 20,000 feet" is a bit unfair because the second aircraft might have a very impressive rate of climb for the first 1,000 feet.

Flight characteristics - Speed calculation and Actual

Indeed speed comparisons are very tricky. Many still thinks that Bf110 was slower than a Hurricane, in fact it was faster at some altitudes and rarely British Fighters made their claim top speed. 

For example, during test in 1940 Hurricane Mk I's averaged 315mph as opposed to 340mph advertised and Spitfire about less than 360 as opposed to 369mph advertised. 

Many German Pilots swore that Me109E was faster than Spit Mk I (on paper about 10mph or so slower) 

The difference lie in acceleration. Bf110 was faster than a Hurricane but took a lot of time to get there where as British fighters has good acceleration. And when you are turning and looping you can't make the level top speed. The best way to get faster is to dive and it is another virtue not much relating to level speed. 

Perhaps max. level speed does not matter that much what matters is acceleration, drag to lift ratio, diving and climbing. Even still valid today. New generation aircraft are all have slower top speed. (F22 Mach1.7, JSF about 1.5, F18E/F Mach 1.7 however good old Mig23 do well over Mach 2... for a few minutes so it has no operational value)

Friday, August 14, 2015

Kayaba Ka-1

The Imperial Japanese Army became interested during the late 1935 in autogyro developments taking place in the USA and, believing that such an aircraft might be developed for use as an artillery spotter, imported from America in 1939 a Kellett KD-1A. However, soon after this aircraft had arrived in Japan it was irreparably damaged during a flight test and the army arranged for the wreck to be transferred to the Kayaba Industrial Company, which had been carrying out research into the autogyro configuration. Shortly afterwards Kayaba was requested to proceed with design and development of a two-seat autogyro based on the Kellett. The resulting Kayaba Ka-1 prototype comprised a fuselage with two separate open cockpits in tandem, a tail unit incorporating a tailplane with twin inverted fins, fixed tailwheel landing gear, and an Argus As 10c engine mounted conventionally in the nose of the fuselage to drive a two-blade tractor propeller; the pylon for the three-blade unpowered rotor was incorporated in the fuselage structure, mounted just forward of the front cockpit.

First flown on 26 May 1941, the Ka-1 proved successful in early flight testing, and the type was ordered into production to serve in the originally intended role as a spotter-plane for artillery units. At the same time Japanese shipping losses were beginning to rise and it was suggested that the very short takeoff required by such aircraft would make them suitable for operation from the light escort carrier Akitsu Maru. A few production Ka-1s were modified for this role and equipped to carry two 132-lb (60-kg) depth charges, but because of their limited payload capability these had to be flown as single-seaters. Operating for some time off Japanese coastal waters they were the world's first operational armed rotary-wing aircraft, with production of both versions totalling approximately 240. This number included one Ka-1 KAI which was tested with rockets attached to the rotor tips in an attempt to improve payload capability, and a single aircraft that was evaluated with a 240-hp (179-kW) Jacobs L-4MA-7 7-cylinder radial engine, allocated the designation Ka-2.

Technical data for  Kayaba Ka-1
General characteristics
    Crew: 1-2
    Length: 9.2 m (30 ft 2⅛ in)
    Rotor diameter: 12.2 m (40 ft 0¼in)
    Disc area: 117 m² (10.9 ft²)
    Empty weight: 775 kg (1,709 lb)
    Max takeoff weight: 1,170 kg (2,574 lb)
    Powerplant: 1× Argus As 10c air-cooled inverted V8 engine, 180 kW (241 hp)
    Maximum speed: 165 km/h (89 knots, 102 mph)
    Cruise speed: 115 km/h (62 knots,71 mph)
    Range: 280 km (151 nm, 174 mi)
    Service ceiling: 3,500 m (11,500 ft)
    Rate of climb: 5 m/s (980 ft/min)
    1x 60 kg (132 lb) depth charges