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Harvard III questions - access hatches (06th Aug)


RidgeRunner

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Re BT-14 to NA.64 : the engines  are in a different position, those of the NA-64 being high as on the BT-9, whereas the BT -14 has it mounted lower with a distinct droop to the nose.  They should be counted as different for production purposes.

 

The changes made from the  NA.16 to the Oak differ in appearance from those in later North American variants, but follow the same logic in changing the outer wing and the tail to improve its stall/spin behaviour.  The engine is changed to one available in Japan.  The rear canopy change is purely cosmetic.  The centre-section of the wing and fuselage appear externally identical.  If its internal structure is indeed completely different then this may change my opinion, but otherwise the aircraft appears to be a modification of the NA.16 design closely equivalent to that of the BT-9 to the BT-14.

 

The Hagedorn book took its 3-view of the Harvard Mk.I from Air Britain's The Harvard File, which I suspect was originally done for Aviation News - agreed about the wrong mainplanes.

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1 hour ago, Graham Boak said:

Re BT-14 to NA.64 : the engines  are in a different position, those of the NA-64 being high as on the BT-9, whereas the BT -14 has it mounted lower with a distinct droop to the nose.  They should be counted as different for production purposes.

They are definitely counted as different for production purposes, the usual problem with such an extensive family is the judgement call of whether it is a new model or simply the (export) version of an existing one.  Things like the differences between the BC-1A and the AT-6 is another, there seems little change in the aircraft, more the air force reclassifying it

1 hour ago, Graham Boak said:

The changes made from the  NA.16 to the Oak differ in appearance from those in later North American variants, but follow the same logic in changing the outer wing and the tail to improve its stall/spin behaviour.  The engine is changed to one available in Japan.  The rear canopy change is purely cosmetic.  The centre-section of the wing and fuselage appear externally identical.  If its internal structure is indeed completely different then this may change my opinion, but otherwise the aircraft appears to be a modification of the NA.16 design closely equivalent to that of the BT-9 to the BT-14.

Japanese Aircraft of the Pacific War by Francillon versus United States Military Aircraft since 1909, Swanborough and Bowers
K10W1, 600 HP engine, wingspan 40 feet 6.375 inches, area 240 sq feet, length 29 feet, height 9 feet 6.625 inches, 3,254 pounds empty
BT-9B, 400 HP engine, wingspan 42 feet, area 248 sq feet, length 27 feet 7 inches, height 13 feet 7 inches, 3,314 pounds empty

 

The engine change BT-9B to BC-1 looks to have added around 200 pounds to obtain the extra power and you would expect a similar increase BT-9B to K10W, which would make the K10W structure around 10% lighter than the BT-9B without engine.


BC-1, 600 HP engine, wingspan 43 feet, area 225 sq feet, length 27 feet 9 inches, height 14 feet, 4,050 pounds empty
AT-6A, 600 HP engine, wingspan 42 feet, area 254 sq feet, length 29 feet, height 11 feet 9 inches, 3,900 pounds empty

 

The internal structure change reports comes from the web pages, Francillon says "extensively modified" without stating exactly what changed.  Does the Hagedorn book mention the K10W and, if so, why it was excluded?

1 hour ago, Graham Boak said:

Nothing here.

You do understand there are now children awaiting a rabbit to emerge from the hat?  Chocolate from a pocket would be a suitable alternative.

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