Nido

The ground speed is the actual speed over the ground (think of a car speedo, doesn't matter what the wind is doing it still reads how fast you are going along the tarmac).

The speed including head / tailwind is the IAS (indicated air speed), i.e. how fast the air is hitting the front of the aircraft

Diesel

Maybe it was MPH Nat?

You have all done my head in btw!

I always thought if the world was rotating 'towards' you (i.e. flying East) then you got to where you were going quicker? I.e ADD the speed that the earth rotates toward you to the forward speed of the plane? Now if the earth rotates at 1000mph at the equator, why ever fly West??? Must be quicker to fly East the 'long way round' if you get a 1000mph free boost

Obviously I havent the foggiest here!!!! Any good links/info aviators?

Cheers

D

bugeyeandy

If the earth rotated and the atmosphere didn't then you would get your 1000mph free boost. It'd also be a tad windy and we'd all be living underground

Diesel

Or the speed it is hitting its **** and increasing its forward total speed by that factor- effectively boosting the engine's max forward mph by that amount? Like downhill on a bike



D

Diesel

LOL! Makes sense!!! But do I get to my house quicker flying East or West (wherever I live!)? D

bugeyeandy

West to East is quicker thanks to the Jetstream.

Sonic'

It took our flight 2 hours longer due to the 200mph headwinds for the majority of the trip going, coming back we had approx 85-100mph tail wind, so gained about an hour, however we were delayed 3 hours leaving as we sat in the queue for the de-icer

Sonic'

Thats what I was thinking, but was sat on the plane trying to work it out, as the book said maximum speed was 560mph yet we were doing 667mph albeit with a 100mph (give or take) tail wind

I remember reading quite some years ago about 747's having to stay above 400mph otherwise the engines could stall (it was to do with the parachutists over Russia jumping from 747's and due to the speed it took 5 miles for everyone to jump out of the back)

So naturally I got a tad concerned when our speed started dropping to 350mph, and got as low as 330mph for a short while and we dropped to 30,000 feet and climbed to 33,000 once we picked up a little more speed

Diesel

Could Einstein pop along with his torch on a rocket explanation please?

Leslie

As Nat says, it is the indicated air speed (IAS) which is of significance to the aircraft. Its needs air moving over the wings at more than a minimum speed to be able to get enough lift to fly. If it needed say 150 Knots minimum IAS to fly it would depend on its height what the actual or true air speed (TAS) is. As you go higher because of the lower air density the TAS will increase in relation to the IAS. At 40K feet you could have an IAS of around 200 Knots but a TAS of over 400. In still air the ground speed would also be say 400 knots but if you had a head wind of say 100 knots then the groundspeed would be 300 knots, or a tailwind of 100 knots would mean a groundspeed of 500 Knots.

We used to have to do a slow flying exercise when i was training on Harvards which meant we could get an IAS of about 45 knots or so before it stalled. We used to get Chinook winds there in Alberta at anything up to 70 knots and it was strange to see a Harvard flying backwards in relation to the ground!

Les

zip106

I thought they'd found out what brought the plane down....
(I'll probably get infracted for this, but what the hell)

http://s252.photobucket.com/albums/h...th_unknown.jpg

DaveD

iTrader: (2)

The preliminary report by the NTSB states that they have found numerous impact marks on the wing leading edges and apparent soft body damage to the engine that's still attached.
They have taken samples for DNA analysis, so provided they don't come back as 'chimp' (DNA samples notoriously get contaminated by the person who took them!) they should point to the culprit for the incident.

FlightMan

Indicated airspeed is a great thing.

At LHR a year or two ago, we had mega strong westerlies wind blowing, in excess of 60mph. Aircraft on final approach were only just moving faster than cars down the M4.

An ATC'er explained IAS to me, and I said " So what happens when the wind stops, and the aircraft is doing the correct 160kts IAS, but 60kts of that is the headwind? "

His answer was the plane falls out of the sky.

Remember that when your coming into LHR on a windy day!

Nido

That's what TOGA power is for

Fuzz

That's exactly what happened to me on the approach to Ayres rock airport a few years ago, not sure whether it was the hot updrafts that dissipated or a head wind changing direction. All I know is the plane was coming in nice and smooth to start with, then dropped like a stone, the engines went to full power and then some, then we hit the dusty bit at the start of the runway
Surprising how quiet the cabin went while everyone swallowed their stomachs.

TopBanana

Don't they come faster in that situation, to allow for the wind dropping?

FlightMan

Nope. As I understand it, IAS is 160kts on final approach, period. It must work OK, apart from BA038 last Jan, ( and that wasn't a wind issue ) we don't have aircraft dropping out of the sky on a regular basis.

J4CKO

iTrader: (1)

TOGA ?

FlightMan

Very good Jacko but I think you know what TOGA is.


For those that don't it's takeoff/goaround. Capt pushes a button and wahey, up you go!

Leslie

Theoretically what he says it right Flightman, if the wind did drop that instantly the inertia of the aircraft would not allow it to accelerate quickly enough to regain sufficient IAS. Practically speaking a 100 knot wind drop does not happen but as Fuzz found out, if you are close to threshold speed which is not that far off stalling speed,a significant windspeed drop can be pretty embarrassing at times.

It used to happen at Malta on the old runway which we were forced to use
in a crosswind from the right. They would not allow us to use the brand new runway. There used to be sudden extreme turbulence at 500 feet on the approach where you could lose 20 knots+ which used to smooth out but it would come back even worse at about 100-150 feet if you were not ready for it. It did cause a disastrous Vulcan crash a good few years ago. The aircraft fell into the undershoot with the co pilot flying it and the runway lip destroyed the starboard undercarriage leg. The captain went around but the APU in the undercarriage bay was burning and the aircraft blew up! Only the Captain and the co pilot survived.

Les

FlightMan

Thanks for your inpout Les. Always good to hear from someone who's been at the pointy end!

As for the Vulcan crash, what a tragedy.

SwissTony

iTrader: (19)

Why it pays to fly first class…..


"Ladies and gentlemen, this is your captain speaking.
All you folks in coach, please immediately exit the plane on the starboard wing and stand in 35 degree water up to your knees.

First class passengers, please exit through the galley where we have a Zodiac 650 inflatable raft and continental breakfast waiting for you."

Leslie

You don't miss a trick do you Swiss!

Les

SwissTony

iTrader: (19)

The eyes are failing but the heart is willing

Leslie

Good thinking!

Les