The great big "ask an airline pilot" thread!

amen wrote: »

You'd need to be travelling at a few kilometres per second to have to worry about that.

No you wouldn't

I think the poster who asked the question had an image of an inflight cruise control in mind when they pondered the aircraft diverging due to surface curvature.

Why. The height is relative to the ground/sea. As such its not a straight line, as I think you are visualising it. It follows the curvature in general.

Well I know its following the earth's curvature but I wanted to know how the autopilot determine when/if a change we required to ensure the correct altitude was maintained by following the curvature.

Taking that that the earths curvature is roughly 0.2m per KM ie. if I start at point A and walk at a tangent to the earth then after walking 1000m I should be 0.2m above the surface of the earth.

So if the plane flies 5000KM (Transatlantic) starting at 10,000m then at the other end if should be at 11,000m allowing for level flight.

If my calculations are correct then at which stage does the autopilot correct the plane to ensure altitude is maintained at 10,0000m?

The aeroplane maintains level flight with respect to the altimeter which is set to air pressure (flight level). Above 3000ft we set to pressure altitude (flight level) by using a common pressure level 1013HPa (mb). This also ensures common separation from other planes. So in theory the plane could raise and lower during the complete flight as it moves from regions of differing pressures but still maintain a constant flight level.

APM wrote: »

Weissbier wrote: »

The aeroplane maintains level flight with respect to the altimeter which is set to air pressure (flight level). Above 3000ft we set to pressure altitude (flight level) by using a common pressure level 1013HPa (mb). This also ensures common separation from other planes. So in theory the plane could raise and lower during the complete flight as it moves from regions of differing pressures but still maintain a constant flight level.

Just to correct the pilot above, we set QNE (1013) once above the transition altitude or cleared above the transition altitude, which is different for each airfield - not 3000ft everywhere, for example...Dublin is 5000ft, Madrid is 13000ft, all of USA is 18000ft. The TA is set by the local aviation authority with regard to terrain and remains fixed, where as the transition altitude will change based on the local QNH.

Thanks for the correction, you are correct! The 3000ft is a UK common Tranistion Altitude. I meant to only use this as a simple example to aid the explanation of the importance of the alitmeter maintaining a standard flight level but equally having varying actual altitude. I see some others are getting confused with some of the codes. Please see below.

QNH
This is the vertical distance above the ground in feet and is referred to as Altitude. And correctly in Ireland is used below 5000ft.

QFE
This is the vertical distance above a particular point of known pressure setting eg. an airport. So with the QFE set while at a particular airport and on the ground your Altimeter will read 0ft. This is rarely used.

QNE
This is the vertical distance above the international standard pressure 1013.25HPa (mb). This is used above Transition Altitude (5000ft) at the next available Flight Level. The first available Flight Level will also be known as the Transition Level. This in Ireland is generally FL60, but can be higher if there is a very low pressure over the region, i.e. the Transition Level in theory can change from day to day (although rarely does).

TA
Outta LHR/LGW and all the other airports I operate from in UK the TA is 6000ft. 6 is usually a stopper on uk sids. With Oilland we just set 29.92 usually outta MSA which is actually the correct setting not 1013 when cleared to a FL as all DUB sids are. .

Been to La Paz in Bolivias classic place where QNE was used on Landing but now use NH with a DA of 13330 ft.

As stated Qne is nothing to do with Flight Level.
Thank Gawd noone uses the "fox echo" anymore.

On a seperate note, you may see a few CO/UA 762s here soon and maybe a Triple7 before Paddys Day. Yet to be loaded into system but planned.

xflyer wrote: »

QNE
This is the vertical distance above the international standard pressure 1013.25HPa (mb).

Not quite, I refer to my post above.

In fact QNE is the reading on the altimeter at touchdown with 1013 set on the subscale.

Having just checked I find the incorrect definition is all over the internet including the ever inaccurate Wikipedia.

You don't set the QNE, you read it from the altimeter on the ground with 1013 on the subscale. 1013.2 is simply the standard pressure setting. No Q code.

I'm interested. Are you saying the QNE is the 'altitude' read off the altimeter on the ground when standard pressure is set, i.e QNE can be different at different airports? I must admit my reference's are from memory, ' A Pilot's Guide to Irish Aviation Law, John Swan, 1995' and my now very old Trevor Tom books. If I'm wrong I'd like to know more! Thanks.

xflyer wrote: »

Yes indeed, that's the true defintion of QNE. The QNE will be different at different airports. But many believe it's refers to 1013.2. It's a very common misconception. Boeingboy pointed out an example of where QNE is used. La Paz is so high that you couldn't set the QFE as the subscale doesn't go that low. So 1013 is set and the QNE used. Another time it might be used in when pressure is so low that again the subscale cannot cope so 1013 is used.

Rare enough events though.

Thanks for that reply, we're all learning.

Irlandese wrote: »

What has been the response of pilots to the suicide of their ryan air colleague as a result of his inability to take the strains imposed on him by their crazy super-stressful flying regime for pilots ?

Do you care to elaborate on the highlighted?

BowlingLad wrote: »

Cessna why do you appear to take offence to the part of the sentence you have highlighted?

5 days of early shifts, 4 sometimes 6 sector days, 25 minute turnarounds. Pilots commuting all over Europe on their off days!! Not sure "crazy super stressful" is the correct term, but it ain't easy that is for sure. They do not earn or get half as much rest as their CEO might like to claim!

I'm just intrigued.

Irlandese wrote: »

What has been the response of pilots to the suicide of their ryan air colleague as a result of his inability to take the strains imposed on him by their crazy super-stressful flying regime for pilots ?

And wheres the proof his work lifestyle drove him to this??? Get a grip and stop speculating

Funny one here,
I was driving along the (windy) m50 today and could feel that i was driving into a 'head wind' so to speak and thought to myself im doing 120kmh but with the wind blowing towards me i wondered what my airspeed would be:rolleyes::o.
But that got me thinking, have any pilots here got any funny stories from when you were driving but went to do something pilot related?

Request permission to leave the motorway?:D Reduce/increase flaps when you speed up/slow down etc?? :P

I sometimes try to fly a tight formation with a car in the other lane of the motorway.

But it's car habits than can transfer like trying to steer aircraft on the ground with the yoke. Or looking for the brake pedal in the middle of the rudder pedals. Then applying the handbrake by lowering the flaps.:o

Depends on which type of aircraft you're on!

I remember someone on here say on the Airbus there is a "ding" in the cabin when the gear is selected up or down.

My own experience is release cabin crew at 5000 feet in the climb using the seatbelt switch and then release the pax above 10,000 if safe to do so. Same again in the decent.

John_Mc wrote: »

3 chimes usually means you're 10 minutes to landing.

3 chimes (almost a chirruping sound) on the A320 series indicates that the autopilot has been disconnected!