What is it that you pilots are wary of when flying in the vicinity of a fuel dumper?

Is it that you think that injestion by your engines will result in something catastrophic or is it because your ECS system will become contaminated or both?

Similar doubts were investigated by the USAF re the fuel dumping from an F-111 and would the afterburners light up the dumping fuel. Test revealed that the flame front of the dumping and burning fuel never reached closer that a few feet from the dumping exit between the engine/afterburner exhaust nozzles. Hence the F-111's spectacular dump and burns.

During inflight drogue and probe refuelling trials I wanted to know the result of an emergency decouple with fuel flowing. One of the results was unexpected.

Copious fuel flowing from the drogue after the decouple immediately completely covered the nose of my aircraft eliminating outside vision for longer that I would have liked in close proximity to a tanker.

The real concern quickly manifested itself as the pressure cabin became filled with a very thick mist of fine fuel droplets which must have been on the edge of being explosive.
Fortunately the mist soon disappeared out through the cabin air dump valve.

I did not notice any "hick-up" from the inboard wing root engines (Valiant) even though they had just injested a whole bunch of raw fuel which produced the cabin misting via the compressor air bleeds.

The cure to the cabin misting potential disaster was to close off the bleeds from the inboard engines during air refuelling operations. Engine injestion became ho hum.

...By the RAAF's F-111. I've not heard of any efforts by the USAF, to do so, and I thought (and am happy to be corrected) that it wasan Aussie innovation.

JDK

Considering that the fuel dump by an F-111 was to rapidly reduce weight following a heavy take off involving a substantial loss of thrust the USAF test centre at Edwards AFB very carefully and with some initial trepidation determined that the flame front would not get close enough to singe the back end.

I believe the resident RAAF TP at Edwards was involved and was able to reassure the RAAF on all counts of safety.