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Thoughts / questions on Jetman's (Yves Rossy) wing

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sam

Member
Joined
Jun 22, 2009
Messages
12
Location
USA
Jetman's wings have changed over time, and I've been wondering why.

Early:

https://lightweightaircraftassociation.wikispaces.com/JetMan
http://www.theblaze.com/wp-content/uploads/2011/05/AP091125012590.jpg

Today:

http://darkroom.baltimoresun.com/wp-content/uploads/2013/11/AFP_Getty-524388490.jpg

Planform:

His first wings looked like they had significantly more span (I would guess close to 3m) and aspect ratio, while today's wing is reported to be 2m. In addition, the early wings had little sweep while the current wing is incredibly swept. Given that his speed range is quite subsonic (almost identical to a Van's RV), this seems odd to me.

At these speeds, a high(er)-aspect ratio, unswept wing seems to be optimal, yet he went the other way as his design evolved. In addition to the aerodynamic drawbacks, the more swept wing has a greater chord in the inboard section, requiring metal plates to protect it from the heat of the jet engines.

Why would he do this? The only things I can think of involve integration with the canopy pack when flying (pulling the inboard section closer to his head allows fairing it in more smoothly) or canopy deployment (a shorter span, more swept wing is less likely to catch or foul a riser)


Wing loading / stall speed:

Given the published weight of the pack is ~120lbs, plus the weight of the average adult male, plus canopy, his gross weight is in the 150kg range. 2m span and 1m mean chord yields wing loading of 75kg/m^2. Using similar guesses for his airfoil Cl, stall speed is around 65-75mph.

A slightly longer wing would seem to yield benefits here.


Airfoil selection:

Flying High: Jetman Talks Flight, Fear, and What's Next

Here he talks about how his original wing designs were derived from an inflatable and thus too thick and too unstable. Later wings appear to be reflexed. Likely this is to reduce the pitching moment and increase stability. Given that his elevator surface is his feet, there's a good chance that his airfoil is a flying wing type with positive pitch stability. If so, this would reduce his max Cl, increase Cd at higher Cl, and increase his power demands.

Again, this would seem to be an argument for more span and less sweep.

What am I missing?
 
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