Ki 51 Method of use

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Brady
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Ki 51 Method of use

Post by Brady » 12 Dec 2023 01:55

It is my understanding that the Ki 51, did not have a bomb sight, for use in level bombing (did it?), but also was not a dive bomber, but rather conducted shallow angle dive attacks, but this is more deductive reasoning than anything else.

Does anyone know definitively how the Ki 51 delivered its ordnance?

Image

Image

I am interpreting this to mean that, the Ki 51 could carry:

2 x 100 kg
or
4 x 50 kg
or
12 x 15 kg

But What "?" is on the outer mount an additional 15 kg of some kind of marker bomb?

Image

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fontessa
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Re: Ki 51 Method of use

Post by fontessa » 12 Dec 2023 09:47

Brady wrote:
12 Dec 2023 01:55
It is my understanding that the Ki 51, did not have a bomb sight, for use in level bombing (did it?), but also was not a dive bomber, but rather conducted shallow angle dive attacks, but this is more deductive reasoning than anything else.
Yes, like Ki-43 and Ki-44, Ki-51 conducted shallow-angle dive attacks. I guess they used Type 89 Sighting Glasses for Machine Guns when dived. It originated German shooting site. Type 95 Shooting-bombing Site for IJN Val also originated it.

99式襲撃機 照準器.jpg



Brady wrote:
12 Dec 2023 01:55
But What "?" is on the outer mount an additional 15 kg of some kind of marker bomb?

Image
The Japanese caption near is 特殊装備爆弾吊架 Special Bomb Rack. Both Regular and Special Bombs seem to use the same type of rack. It is reasonable. I think the Ki-51 bomb-dropping system was configured so that regular bombs and special bombs could be dropped separately.

陸軍通常爆弾.jpg

陸軍特殊爆弾.jpg

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Brady
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Re: Ki 51 Method of use

Post by Brady » 12 Dec 2023 16:18

Thanks for that great reference, I am especially curious about the IJA use of SAP bombs as well:

Type 4456 100 kg Skipping bomb
Type 3 250 kg Skipping bomb
Type 4 100 kg Anti-shipping bomb
Type 4 250 kg Anti-shipping bomb
Type 4 500 kg Anti-shipping bomb

TME-1985-4 Covers these in some detail, but the TME reference has proven to be not entirely reliable at times.

I believe Type 4 denoted introduction in 1944, but there was a pre war SAP bomb used by the IJA

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fontessa
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Re: Ki 51 Method of use

Post by fontessa » 20 Dec 2023 06:30

fontessa wrote:
12 Dec 2023 09:47
Brady wrote:
12 Dec 2023 01:55
It is my understanding that the Ki 51, did not have a bomb sight, for use in level bombing (did it?), but also was not a dive bomber, but rather conducted shallow angle dive attacks, but this is more deductive reasoning than anything else.
Yes, like Ki-43 and Ki-44, Ki-51 conducted shallow-angle dive attacks. I guess they used Type 89 Sighting Glasses for Machine Guns when dived. It originated German shooting site. Type 95 Shooting-bombing Site for IJN Val also originated it.

fomtessa
The above answer was not thoughtful enough. When we look closely at the drawing you uploaded, there is a "Bomb Sight" in addition to the "Gun Sight". As shown in Figure 1, this Bomb Sight was not present on the K-43 and Ki-44. Even though the Ki-43 and Ki-44 could carry bombs, there were almost no such cases. Figure 2 shows the Ki-51 cockpit in front of the pilot. To the right of the Gun Sight was the Bomb Sight's Rear Sight, and in front of it was the Front Sight. Rear Sight could be moved up and down. If the Rear Sight was located higher than the Front Sight, the pilot would have been looking "downward” through the Bomb Sight. For example, in the case of the Type 94 bomb, as shown in Figure 3 (there was no other suitable diagram), (1) Angle of descent 60° (2) Airplane speed 400 m/h (3) Bomb Release Altitude 500 m, the angle deviation was 4°48". The relationship between this "angular deviation" and the extension value of the Rear Sight was already tabled, so rise the Rear Sight according to this table, the bomb will hit the target by the aiming with the Rear Sight. In Figure 3, Black figures (60°) and (450m) were for IN\JN Val.

Ki-51 1.jpg

Ki-51 2.jpg

Ki-51 3.jpg
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Brady
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Re: Ki 51 Method of use

Post by Brady » 20 Dec 2023 15:42

Thank you for that very detailed explanation, it sounds to me like this plane is essentially a dive bomber but without dive brakes?

Which suggests that it could not sustain a dive for as long as the D3A could, but that it would’ve been far more accurate than a plane without such a sight, I think the question then is how much more accurate was the D3A, or maybe a better way to look at that is that the latter would’ve been more survivable when operating against ships because it would’ve been able to sustain a higher release from a higher altitude, but that the weapon delivery itself likely would’ve been as accurate?

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Re: Ki 51 Method of use

Post by fontessa » 22 Dec 2023 17:34

Brady wrote:
20 Dec 2023 15:42
Thank you for that very detailed explanation, it sounds to me like this plane is essentially a dive bomber but without dive brakes?
Yes. Like the A-10 Thunderbolt II "Warthog", the K-51 was tasked with close ground support. It was intended for low-altitude operations, and high-altitude performance was not required. Therefore, dive brakes were not required for it's dive bombing.


Brady wrote:
20 Dec 2023 15:42
This suggests that it could not sustain a dive for as long as the D3A could, but that it would’ve been far more accurate than a plane without such a sight, I think the question then is how much more accurate was the D3A, or maybe a better way to look at that is that the latter would’ve been more survivable when operating against ships because it would’ve been able to sustain a higher release from a higher altitude, but that the weapon delivery itself likely would’ve been as accurate?
As posted before, the bombsight of Val originated from German shooting sites like Ki-43 and Ki-44. But it was reformed for dive bombing as shown in Figure 1. For dive bombing, the angle deviation was carved at 10m intervals when looking at the sea surface at a bomb release altitude of 650m and a descent angle of 60 degrees. The vertical direction was used in the same way as the Ki-51. The lateral direction showed deviation due to crosswinds. The pilot must keep looking at the bombsight and could not see the altimeter, so the second seater crew read out the altitude one by one. This would have been the same with the Ki-51. Despite this poor bombsight, the Val had a formidable accuracy rate at the beginning of the war. It was the result of intense training. Take the sinking of HMS Cornwall off Ceylon as an example. At this time, Val companies of Akagi, Soryu, and Hiryu were dispatched, and got a bomb hit rate of 15 / 16, 14 / 18, and 17 / 18, respectively. Figure 2 shows Hiryu company's hit points. What should be noted is that Val's path was not along the target’s axis, where a high hit rate could be expected. It was oblique to the target. This period was the peak of Val's glory.

Ki-51 bombsight.jpg

Cornwall.jpg


Correction, Sorry
I have translated Kani 特殊装備爆弾吊架 Special-Bomb Rack. But it should have been translated as Special Bomb-Rack. When the Ki-51 hung 15kg bombs and had the sky, the innermost bombs were blocked by the sky and could not be dropped. The main wheel spats were shaped so as not to interfere with bomb dropping, so there was no problem. Thus, for the innermost bombs, the Special Bomb-Racks were placed in the outermost positions. This means that under normal conditions the Special Bomb-Racks would not be used. (The rack itself was "ordinal", but it was added for "special" purposes when skis attached)


KI-51 そり.jpg

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Re: Ki 51 Method of use

Post by Brady » 22 Dec 2023 22:57

This is very intriguing, most sources indicate that the KI 51 was not a dive bomber, but clearly it appears to be very much the case, it’s just that it did not operate from such altitudes that required it to use dive brakes…

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Re: Ki 51 Method of use

Post by Brady » 22 Dec 2023 22:58

This is very intriguing, most sources indicate that the KI 51 was not a dive bomber, but clearly it appears to be very much the case, it’s just that it did not operate from such altitudes that required it to use dive brakes…

Was this also True of the KI 30?

Presumably this is why the KI 48 in its later models was designed with dive bombing in mind because it was intended to replace the KI 51?

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Re: Ki 51 Method of use

Post by fontessa » 23 Dec 2023 16:24

Brady wrote:
22 Dec 2023 22:58
Was this also True of the KI 30?
The Ki-30 was classified as a light bomber. It could carry more bombs and fly farther than the Ki-51. Although it did not have dive brakes, it could also dive bomb. However, unlike the -51, the lower part of the fuselage was not armored. Experience with the Ki-30 contributed greatly to the success of the Ki-51. (23,000 Ki-51s were manufactured, including the reconnaissance version)

Brady wrote:
22 Dec 2023 22:58
Presumably this is why the KI 48 in its later models was designed with dive bombing in mind because it was intended to replace the KI 51?
At the require of ground forces, the Ki-48 had a dive brake and was capable of dive bombing. However, I don't know how the ground forces intended to use it. Incidentally, the Navy's Ginga also had a dive brake and was capable of dive bombing. I think it was somehow inspired by the Luftwaffe...

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