IAS with headwind increase

[fredgrav]

Hi everyone,
a doubt raised while reviewing GS Mini function and headwind effect on IAS: as far as I know an increase in headwind would cause the speed trend (IAS) to go up, but only if no vertical acceleration's allowed with increasing lift (no altitude change). This way, the energy coming from HW, is converted into a horizontal acceleration (IAS increase). At that point I was asking myself if there was any other effect (beyond "inertia" and compressibility) acting on the pitot tube reading with increasing headwind, my belief is ... the greater the headwind, the faster the quantity of ram air impacting the tube, the higher the IAS reading, am I right ?!

Every answer's widely appreciated,
fredgrav

[Loose rivets]

How long do you anticipate this increase in IAS will last?

[Ex FSO GRIFFO]

Only 'momentarily', until the aircraft once again achieves equilibrium I would expect.....
The extra headwind 'speed' would cause extra drag etc etc

The larger (heavier) the aircraft, the longer the 'moment' because of the higher inertia factor.

[ekwhistleblower]

If the aircraft was attached to the ground the IAS increase/ decrease would last for as long as it was windy. In the air as the plane isn't tied down just the ground speed will decrease with IAS remaining the same as the wind speed increases and hence the IAS target is increased in the computer to maintain the groundspeed at a safe level in case the wind stops / changes direction. A party ballon isn't flying through the air it is flying with it; IAS zero, Groundspeed = Windspeed. Now if you are trying to go to a macro level become a scientist, buy a microscope and forget flying for a career.

[Ex FSO GRIFFO]

Hi Mr e,

Howabout in a 'windshear' situation where the aircraft transits from one W/V to another 'suddenly' as in a change of alt.?

The original query was about a 'theoritical' situation I would think....

We all know in practice, except in some windshear situations, some well documented, it doesn't matter much.....

[fredgrav]

How long do you anticipate this increase in IAS will last?

Hi Loose rivets,
we can't predict how long the IAS increase will last, that's the principle of implementation of GS mini (where actual wind is given by ADIRU's), just to keep energy high in spite of SUDDEN changes in headwind component.

[rudderrudderrat]

Hi fredgrav,

my belief is ... the greater the headwind, the faster the quantity of ram air impacting the tube, the higher the IAS reading, am I right ?!

Are you really asking how an airspeed indicator works?

just to keep energy high in spite of SUDDEN changes in headwind component.

It's the VAPP which is increased by GS mini during these wind gusts. The inertia of the aircraft maintains the present ground speed for a while, which results in an immediate increased airspeed during the gust.

[fredgrav]

Are you really asking how an airspeed indicator works?

Hi Rudder,
sure not, simply was trying to figure out how an ASI precisely bahaves with increasing headwind, in a more scientific manner ...