Re: Doughnuts on a rope plane sighting-with request

Message posted by Magoo on May 14, 2000 at 21:11:18 EST:


I wasn't really sure what you were asking - I thought it was just a reported sighting. If you are asking about PDW engines being applicable to commercial use, then the answer is 'sure, why not? In 20-30 years maybe'. If you're asking whether they are in commercial use now, then the answer would be 'no'. There are no commercial airframes in use or in development that could support a PDW engine, nor is there currently the requirement for such an aircraft. There is also no infrastructure in place at airports or maintenance facilities to support the technology.

As far as we 'know', PDW engines work in theory only, and have not been flown on any full scale test vehicle. Some suspect them to be in use on 'Aurora' or whatever, but there has been no hard evidence to support this. I personally doubt whether we have the technical knowledge and materials necessary to support any long term reliable use of such an engine, although as an aviation technology geek, I would be more than pleased to be proved wrong.

Conventional turbofan and ramjet technology is being continually refined to the point where the short-term benefits of full scale development of PDW engines is questionnable. In the longer term, as near-earth orbit capable commercial or military vehicles come on line, then perhaps it will become viable then.

The 'doughnut on a rope' contrail phenomena has been explained in the past in this forum, and can be caused by variable winds at altitude, or by power variations or fluctuations being applied to the aircraft itself. It is not a phenomena associated only with PDW engines.

I hope this answers your question. If you can think of anything else unusual about your sighting, please don't hesitate to post it.


In Reply to: Re: Doughnuts on a rope plane sighting-with request posted by Jeff on May 13, 2000 at 19:34:29 EST:


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