Ka-2b Pilot
From the Hunter T Mark 7 Air Publications A.P. 101B-1302- 1, Chapter 2, Fuel System,
18. Under certain conditions of flight, particularly during inverted flying, air may pass into the front tanks. Air also comes out of solution from the fuel at altitude, or the fuel may boil. The expansion of this air or vapor while climbing may prevent fuel transfer and allow the front tanks to empty while fuel remains in the other tanks To prevent this, a vapor release valve is fitted to each front tank.
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Thus, when the warning indicators show, the contents of the front tanks only are indicated, this being the only amount of fuel available to the engine.
and
From the Pilot's Flight Manual, section 1-1, page 9, paragraph 18, Fuel Gauge Errors: "The fuel contents gauges have been found to give erroneous indications due to temperature effects on the electrical gauging system. The magnitude of the error depends on both temperature and flight conditions. Low temperatures at high altitude give gauge underreading; high temperatures at high speeds at low altitude give gauge overreading. During a descent from altitude, if the inaccuracy is a gauge under reading, the gauges progressively become more accurate and may eventually tend to overread."
Given that the pilot is still alive, I'd hope that some of the controls and gauges will be intact and give the authorities some factual info to determine cause.