A320 VS1G and conventional Stall speed
Thread Starter
Joined: Dec 2008
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From: Birmingham
A320 VS1G and conventional Stall speed
Guys,
Can anybody explain me in simple Terms how the 320 VS1G Speed is calculated or what it actually means?
I know that Airbus presented a new stall Speed which corresponds to the 1G flight path just before the actual stall. So am I right if i can say: Airbus because of the protections in the System can lower the relevant Speed and thats why we have the factor 0,94?
Sorry guys have a mental blockage right now
Can anybody explain me in simple Terms how the 320 VS1G Speed is calculated or what it actually means?
I know that Airbus presented a new stall Speed which corresponds to the 1G flight path just before the actual stall. So am I right if i can say: Airbus because of the protections in the System can lower the relevant Speed and thats why we have the factor 0,94?
Sorry guys have a mental blockage right now
Joined: Jun 2014
Posts: 346
Likes: 1
From: Mordor
Vs1g is the lowest speed, at which the airplane can maintain 1g, i.e. level flight. It corresponds to the Cl max
Vs is the lowest speed attained during stall testing of the airplane. The pilots were able to reach this speed lower than Vs1g, but the plane was already losing altitude.
The way I understand it, the certification rules were changed at some point, and new airplanes are required to base their performance on Vs1g, whereas airplanes certified earlier were referencing to Vs.
However, this puts the new airplanes at a disadvantage, as Vs1g is higher than Vs. To counter this, Airbus managed to convince the certifying authorities, to allow for lower margins during performance calculations (eg. Vref is 1.23*vs1g instead of 1.3), because the airplane is speed protected anyway....
P.S. strangely enough, ATR-42/72 also use Vs1g and lower safety margins, even though they are a conventional plane, not speed-protected
Vs is the lowest speed attained during stall testing of the airplane. The pilots were able to reach this speed lower than Vs1g, but the plane was already losing altitude.
The way I understand it, the certification rules were changed at some point, and new airplanes are required to base their performance on Vs1g, whereas airplanes certified earlier were referencing to Vs.
However, this puts the new airplanes at a disadvantage, as Vs1g is higher than Vs. To counter this, Airbus managed to convince the certifying authorities, to allow for lower margins during performance calculations (eg. Vref is 1.23*vs1g instead of 1.3), because the airplane is speed protected anyway....
P.S. strangely enough, ATR-42/72 also use Vs1g and lower safety margins, even though they are a conventional plane, not speed-protected
Joined: Sep 1998
Posts: 1,615
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From: wherever
As I understand it reference stall speed Vsr is the declared stall speed chosen by the manufacturer. It may not be lower than Vs1g which as has been said is the lowest speed for level flight.
During a stall demonstration the aircraft will experience less than 1g and this was when the lowest indicated speed was recorded in previous certifications.
The new requirements appear lower on the surface. 1.23 is lower than 1.3 but it's actually the same margin. 1.23Vs1g = 1.3 Vs.
During a stall demonstration the aircraft will experience less than 1g and this was when the lowest indicated speed was recorded in previous certifications.
The new requirements appear lower on the surface. 1.23 is lower than 1.3 but it's actually the same margin. 1.23Vs1g = 1.3 Vs.
Joined: Oct 2004
Posts: 256
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From: australia
Vs1g came into being about the same time as the A320 initial certification.
Previous stall speed determination was the "minimum speed during the stall manoeuvre".
The problem with this approach was that all aircraft were not equal once flown beyond Cl max. Aircraft with the same Vs1g do not necessarily have the same Vsmin. This was to "level the playing field".
Had this not occurred Airbus could have still demonstrated a Vsmin stall in flight test.
Pretty well all stall testing is done at an approach rate of 1 kt/second, this results in a descent, also the higher the approach rate, the lower the stall speed.
The new factors were chosen to be the equivalent of the previous factors.
Previous stall speed determination was the "minimum speed during the stall manoeuvre".
The problem with this approach was that all aircraft were not equal once flown beyond Cl max. Aircraft with the same Vs1g do not necessarily have the same Vsmin. This was to "level the playing field".
Had this not occurred Airbus could have still demonstrated a Vsmin stall in flight test.
Pretty well all stall testing is done at an approach rate of 1 kt/second, this results in a descent, also the higher the approach rate, the lower the stall speed.
The new factors were chosen to be the equivalent of the previous factors.
