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Blackwing as touring plane

LeSving wrote:

This shows more how “fragile” other planes are. But, 212 kt in a plane weighing 500 kg and with a stall speed of 35? Just touching the stick, and you have 10g in 2 ms A slight turbulence, and it must be a terrible ride.

I got G-meter stuck at 9G after landing in a rough terrain and crossed a plough line, as it was a PC11 aerobatic glider (Pilatus B4: 300kg and 130knts VNE), the explanation did not fly high but one jury confirmed that figures did not look that aggressive but my landing was really fast, luckily I did not lose my teeth on that one

The Pilatus is all metal and rock solid (limits are +7G/-5G) but will show +4G/-2G flying level at 100kts in thermic days (sings like harmonica and cables play guitar), so I think your 10G in 2ms is really plausible at 200kts without even touching the stick

nobbi wrote:

whereas a Vne is always an IAS (indicated airspeed) to be read on your airspeed indicator

Some of the certification requirements for high speed design VNE relate to flutter, this has to be treated as TAS, it is a “frequency” not “amplitude” of aerodynamic forces (these link to IAS as they decay with low density), the red bar on IAS include a cushion factor but it does not mean it is an IAS, I guess this is not an issue for SEP as service ceilings are low? also we will tend to reduce speed when yoke force feedback wiggles for no reason unlike the FBW guys

On flutter and frequencies, this appear more in studying bridges: there is combination of structure shape, mass and excitation frequency where any structure no matter how solid it is will wiggle until it breaks even with low forces, the aircraft will have same airframe-airflow resonance at specific frequencies (more to do with TAS, mass and shape than the amount of aerodynamic force) but there are surely other considerations, for bridges, most are designed to take lot of force but they do fail at the wrong harmonics (Angers bridge case: it could handle the weight of 1 million soldiers but failed with 200 marching in sync)

https://en.wikipedia.org/wiki/Angers_Bridge
https://en.wikipedia.org/wiki/Tacoma_Narrows_Bridge_(1940)

Last Edited by Ibra at 19 Apr 13:31
ESSEX, United Kingdom

Possibly, being uncertified, they can redefine Vne as they wish, without flutter tests etc, no?

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

Possibly, being uncertified, they can redefine Vne as they wish, without flutter tests etc, no?

If it is a manufacturer’s test flight, I guess they can do whatever they want?

ESKC (Uppsala/Sundbro), Sweden

Peter wrote:

Possibly, being uncertified, they can redefine Vne as they wish, without flutter tests etc, no?

I think this is a nice article on the topic of VNE specification (and flutter), the “bad example” was a non-certified aircraft
- Max design for cruise is 33 time square root of wing loading (a “fantastic plastic glider” will have a lower one )
- You multiply that by 1.4 to get max speed on dive VD and 9/10 of that is basically VNE (even aircraft can never achieve that)

From these one can run lab stress on materials and actual flight tests up to VNE including flutter, for certified aircraft you have to show no flutter frequencies occurs between VNE and 1.2*VD but that can be done on computer models, for uncertified people can skip this but the risk can be mitigated by BRS or wearing a parachute flying high speeds with low wing loadings need some courage and determination, in gliders it is hard to ignore those signals as you get past the yellow arc, another good reason to have a parachute…

https://www.flyingmag.com/technique/proficiency/technicalities-are-you-feeling-lucky/

ESSEX, United Kingdom

MedEwok wrote:

I am curious why an aircraft that looks so much like any other plastic/composite SEP is capable of flying way faster than the lot of them.
Super-smooth varnish, no rivets, gear up and all gear covers super-flush to the body, as little fuel as needed, balance to require minimal elevator trim, etc… Above a good general aerodynamic formula (you don’t sit upright like in a C172, cross section is much reduced, wing/fuselage transitions received a lot of attention), the tricks are well known.
To get there they had to fly at MCP, 135hp for the Rotax 915iS. FF at that power was probably like any engine at that power, in the region of 10-11 gph.
It’s still more economical to pull back and fly it around 150-170KTAS but 40% lower FF.

Clipperstorch wrote:

Vne is 170kts
Most importantly, VNE is indicated. They flew level at FL100, where KTAS is >> KIAS.
Last Edited by Arne at 20 Apr 15:31
ESMK, Sweden

“AVIONIK EXPERT”

They could have used Google Translate at least. Anyway, here is the video:



Last Edited by Dimme at 21 Nov 19:03
ESME, ESMS, ESOW

Very good. Meanwhile someone else is cruising at 365kmh – 197kt with a common Rotax 914.

Portugal
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