Concerning the observation glass of Ki-147,
The Mitsubishi document of course tells us that a separate tracking glass is equipped to command the Ki-147 missile. However, pilot testimony of controlling Ki-147 says that to observe the missile “we used only the naked eye” and the exhaust flame was not visible, “only the smoke”. Moreover, they say that despite this “it was possible to lose sight of it but not very frequently”.
Refer to Japanese Aircraft Relative Performance, Serial No. 436, Report No. 2-T in my old suggestion: Mitsubishi Ki-147 & Kawasaki Ki-148, "I-Gō"「イ号」- Japanese Guided Missiles! - Passed for Consideration - War Thunder - Official Forum
First, I think that the bright orange paint of Ki-147 and Ki-148 described in sources given by @tester188 was probably for visual assistance, not just an experimental camouflage. So I would like to see the Ki-148 in orange camouflage in the game.
Both Ki-147 and Ki-148 must have used the Type 94 Surveillance Scope to range the target warship and determine the launch time.
However, I think that the testimonial evidence suggests that the operator did not originally have a dedicated tracking scope to guide the missile. We know that Ki-147 was less accurate than Ki-148 because of its characteristics:
- radar altimeter with limiter did not work on Ki-147
- control deteriorated at the end of flight because of pneumatic power system that depleted when pumping fuel on Ki-147
On the other hand, Ki-148 had a hit rate of 70-80% on large targets. Because of Ki-147’s inferior accuracy in testing, I would theorize that they decided to equip a tracking glass later. There is more space for additional equipment in the nose of Ki-67 than Ki-48II, so I am not sure that Ki-147 + Ki-67 having a tracking scope added means that Ki-148 + Ki-48II also had one. We need visual evidence of course.
Now here is something a little interesting. Mitsubishi’s report states that only the initial 10 prototypes of Ki-147 were built. However, this high-res image of Ki-147 seems to show the serial number ‘11’ on the side:
Here’s a prototype missile showing the serial number ‘2’:
Some sources state that a limited production of a few missiles continued after the initial 10 prototypes, and I think this is true. If so, this photo must have been taken in the later period of testing. If a tracking glass was added, it might be present in this plane, but sadly the nose is not in the photograph.
There is another close angle, but the inside of the nose is indistinguishable for me: