Here is another definition for the debate.
VNE
The VNE , or the never exceed speed, of an aircraft is the V speed
which refers to the velocity that should never be exceeded due to risk
of structural failure, due to calculated factors such as wing or tail
deformation or due to aeroelastic 'flutter' (unstable airframe or
control oscillation). VNE is specified as a red line on many airspeed
indicators. This speed is specific to the aircraft model, and represents
the edge of its performance envelope in terms of speed. Well below the
speed of sound, the VNE is read as Indicated Air Speed (IAS), since the
pitot indication is a direct measure of the dynamic pressure for any
given airspeed. At altitude, where TAS is higher than IAS, aerodynamic
damping is weaker than at lower levels (damping is proportional to IAS)
whereas inertia-induced disturbances are stronger (inertia grows with
acceleration, which is the time derivative of TAS). This condition, if
continued beyond tested limits, pre-disposes to unstable oscillations or
'flutter'. For instance, the TAS/IAS ratio at 40,000 ft on the ICAO ISA
is 2:1, that is, TAS is approximately twice IAS.
Every aircraft I have ever flown stated the Vne as indicated airspeed.
The Falcon 20 I'm away flying at the moment has its Vne and Vno stated
as an indicated airspeed.
Just been to the bar to get a beer and a colleague of mine answered the
question - Vne is in indicated airspeed always. How else would the
pilot know if he were exceeding it. I have some respect for his opinion
as he recently retired from British Aerospace as a Senior Test Pilot, he
flew harriers and did much of the flight testing on the new Typhoon 2
fighter.
I don't know why everyone is getting so hot under the collar about the
flight at Vne. Ivan and Pete Clark did a lot of testing of the europa.
I do it every year at permit renewal as required and it really is a non
event - I must confess however that I cannot see the point of that
particular part of the flight test schedule.
Incidentally, at medium to light weights G-JULZ will achieve Vne
straight and level at 2000 feet (indicated airspeed) 914/Airmaster
'with the pedal to the metal'. Andy Draper found the ASI to reasonably
accurate - I don't worry about it too much anyway.
I don't think we Rotax chaps need to worry too much anyway. It would be
different if we all fitted Jabiru 6s - we could then climb at some mind
spinning rate towards the tropopause and cruise at a Mach No - just to
be cool. Of course we would have to fit a larger fuel tank - wouldn't
we Bob? One distinct advantage of the Jabiru is that at those dizzy
altitudes it can reach you will be able to keep the cabin warm -
apparently many of them overheat or have some type of cooling issues.
Oh! I have slipped the surly bonds of earth
And danced the skies on laughter-silvered wings;
Sunward I've climbed, and joined the tumbling mirth.................
It makes me want to sign on again.
Now don't get upset, just having a bit of a leg pull - you are all
getting far too serious.
regards,
Mike.
"TAKE COVER!!!!..........INCOMING"
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