Thought On The Recent Airbus A330 Crash

[MacGyver]

The focus on the flight 447 investigation is maybe the airspeed sensor tubes iced over and gave inconsistent airspeed readings. Causing the pilots to either fly too fast and break apart, or fly too slow and stall.

I'm wondering why doesn't a multi-million dollar plane like the A330 use GPS for speed info?

 

[Indy]

I'm no pilot but I would think that the biggest reason is the difference between air speed and ground speed.

 

[MacGyver]

I'm no pilot but I would think that the biggest reason is the difference between air speed and ground speed.

The 24 GPS satellites are about 12,000 miles above us. On the ground or in flight, that wouldn't matter.

 

[Indy]

What does a GPS have to do with airspeed?

 

[MacGyver]

What does a GPS have to do with airspeed?

It should be able to calculate airspeed as well. Speed is speed. On the ground or in-flight doesn't matter.

 

[Tinkerer]

Your not getting it.
WIND - ground speed is not the same as air speed when there is a wind.
In a storm with a 50 MPH head wind - ground speed is 550 - air speed is 600

 

[Tinkerer]

If you went with GPS to govern your speed in a plane. You wouldn't know what your TRUE air speed really was. At a certain altitude a plane HAS to maintain a minimum air speed to stay in flight.
I read somewhere that the blackbird at max height had a critical speed variance of only 5 MPH. Too slow and the plane falls out of the sky, TOO fast and the wings tear off.

 

[MacGyver]

Doh...........I missed the obvious one there. I never took in account of headwind/tailwind

 

[Pachanga]

I personally think the pilots were stupid. Who in their right mind would try and fly through a storm towering up to 15,000 feet higher than you can fly? They should have skirted around it or turned around.

God be with all who were lost.

 

[fund razor]

Doh...........I missed the obvious one there. I never took in account of headwind/tailwind

You didn't miss the obvious, you missed the "plane on a treadmill" thread.

 

[Chris]

Aircraft use a combination of systems to determine airspeed and position. GPS and inertial navigation are both elements. Some years back, navigators used dead reconing calculated with data from star position. They would shoot position with a sextant through a portal in the fuselage. Now that's done with INS. Part of the issue here is terminology- airspeed is really only relative to the lift generated by the wings.

People assume that intercontinental flight is just like continental flight. That couldn't be further from the truth. Over land, we have radar coverage everywhere. It can track position and altitude quite accurately and can also provide very fine levels of weather detail. Over an ocean- especially over lesser travelled water, data is much more scarce. Typically pilots must rely upon reports from other pilots and sketchy data. And often there's nowhere to go if something unexpected arises.

 

[outriggers]

At altitude your indicated airspeed might be only 245 knots when you true airspeed is 500 knots. (very thin air and temp-40 C). % of Mach is used at altitude. I think a A330 cruises at .80 to .82 . Differance between high speed stall and low speed stall is very narrow up high, like 15 knots sometimes, as mentioned in a earlier post. This is called Coffin Corner, this is the most efficiant place to operate a jet. It's like balancing on the head of a pin. Speed up, fall out of the sky, slow down fall out of the sky. Doug

 

[Buoy]

You didn't miss the obvious, you missed the "plane on a treadmill" thread.

yep, this one has my head spinning just like the treadmill did at first.
Nick finally explained that one in a way I could wrap my thick head around it.