Full size landings

[fly boy3]

This may be a daft question. When large say passenger jets land, the pilot obviously cannot see directly beneath him to see the Tarmac.Just wondered I'd the plane actually touches down using computors or pilot skill. Thanks.

[Don Fry]

A preordained throttle setting, a preordained airspeed, from the book of instructions that came with the plane, gives a preordained drop rate. And that gives the bump when it hits the runway.

Edited By Don Fry on 01/12/2017 14:27:28

[Chris Walby]

No sure if this is true, but someone told me that the "old" style of touchdowns where the pilot would hold the round out with the objective of as a gentle landing as possible has been superseded by the get it down even if there is a bit of a bump!

The rational is that the longer the flair is held the more runway you are using and the closed to stall/affects of cross winds.

Myth?

[Rob Ashley]

If the autopilot is flying the approach and landing the auto landing system will flare and retard the throttles based on ground proximity (Radar Altitude) against an airspeed schedule with respect to AUW. The pilot effectively does the same but with the human in the loop there is more flex in the rate of descent.

Incidentally, the bump as opposed to smooth touchdown is there to prevent aquaplaning or lateral drift (in drier conditions) to firmly plant the aircraft which also prevents bouncing.

Rob

[The Wright Stuff]

Full size landings...

...even less optional than model landings!

[Pete B]

In cockpit videos one often hears the radar altimeter(?) counting down in 10ft increments, which must help.

Pete

[Don Fry]

My information came from a BA 747 pilot I taught to fly. His explanation that you have little idea of where the ground is when seated that far above it precludes niceties.

Edit, taught to fly models.

Edited By Don Fry on 01/12/2017 15:43:44

[Pete B]

Glad you clarified that, Don......

Pete

[Simon Chaddock]

If you don't mind spending a rather geeky 20 minutes watching 10 landings it does seem not all do exactly the same thing but all do flair (or reduce the rate of descent) to some degree just before touchdown.

The A320 was probably the best 'greaser' but in most cases lowering the nose and opening the lift dumpers causes the undercarriage to squat down rather than any impact with the runway.

From a model flyers point of view what is noticeable is how beautifully constant is the rate of descent on finals!

[Steve Hargreaves - Moderator]

I understood that most airliners land themselves...or rather they are landed by computer. Pilots do however have to do a certain number of landings to "keep their hand in" so to speak.

Allegedly you can tell when the human pilot is making the landing as they are the slightly dodgy & bumpy ones.....I can relate to that....

[Geoff S]

The only full size aircraft I've landed are gliders. I was taught to flair when the height of a double-decker bus above the ground and just hold off gently but I guess a glider's pilot position is a lot lower than that of a 747

Geoff

[Rob Ashley]

Simon,

Yes, when U/C legs squat when the weight of the aircraft is applied to them - i.e. the full weight so when the lift spoilers operate this is the slight sink you feel. The initial bump is the wheels touching down and the acceleration of the wheels to flying speed, but the fescalised portion (the shiny bit) of the undercarriage remains until the oleos are compressed. Bad (heavy) landings will also compress them and they are not always caused by human pilots (note not always Steve ) - turbulence or gusty conditions have say in this too and impact of the Auto Land System (ALS).

All of the 40+ types I have flown in may career do this bump and squat in some form or another. Personally as a pilot I'm not a great fan of the ALS but they do work and are generally more fuel efficient.

Pete - Yes the height talkdown you hear is from the Ground Proximity Warning System (GPWS which is basically a RadAlt).

In lighter aircraft you flare at the appropriate point, not heard of the double decker bus thing before but my experience has led me to deduce that your butt tends to tell you when time is right otherwise the oleos compress too much after the big bump........

[Crosswind]

Couldn't be further from the truth there Steve! I've been flying for UK airlines for over 20 years. The occasional landing is accomplished through the autopilot. These are usually done in poor visibility, i.e mist, fog and perhaps the odd one for recency purposes ( to keep auto land qualifications current ). The vast majority are flown manually, we like to keep our skills up to date! To achieve a consistent landing most airlines have a number of 'gates' whereby the aeroplane has to be in a particular configuration at a point in space. An example; at 1000ft ( approximately 3 nautical miles from the runway threshold ), the aircraft should be in the final landing configuration ( gear down, landing flap selected ). Engines spooled up, landing checks complete and in the correct place ( on the glideslope and in line with the runway ). If these conditions aren't met then a go-around should be made. The trick is managing the aeroplanes energy to meet these criteria! Bearing in mind how weather conditions change day by day and hour by hour, and that's before we add in the complication of speed and height requirements imposed by air traffic control! what we're trying to achieve is to put the aeroplane on the same flight path again and again. Then we can use various cues to land the plane consistently. We want to touch down at the right point on the runway at the right speed. There's an old saying ' a good landing comes from a good approach'. I hope this makes some sense!

[Piers Bowlan]

Posted by Steve Hargreaves - Moderator on 01/12/2017 17:15:12:

I understood that most airliners land themselves...or rather they are landed by computer. Pilots do however have to do a certain number of landings to "keep their hand in" so to speak.

Allegedly you can tell when the human pilot is making the landing as they are the slightly dodgy & bumpy ones.....I can relate to that....

Actually Steve it is the other way round. Although all modern airliners are autoland/CAT3 capable the normal situation is a manual landing off an auto-approach unless the weather is poor (below CAT1) or the equipment is being checked or for training purposes (or practice if your check is imminent). Handling skills are very important which is why aircraft are not routinely auto-landed except for the reasons above.

Another myth debunked!

[Peter Jenkins]

I've noticed that quite a few folk use the term flair when they mean flare. You might flare with flair but just a flair before landing doesn't work! They mean different things. Sorry to be picky!

[Rob Ashley]

Hi Peter. I guess picky depends on your point of view. I have a thing for brought and bought. Don't know why. And yes I have certainly flared with flair before. .....

[Steve Hargreaves - Moderator]

Oooo every day is a school day.....

[Geoff S]

Posted by Rob Ashley on 01/12/2017 19:00:33:
Hi Peter. I guess picky depends on your point of view. I have a thing for brought and bought. Don't know why. And yes I have certainly flared with flair before. .....

Oh dear your (sic) right It's bit like bear and bare. As something of a spelling/grammar pedant I'm mortified My excuse is that when you bought a Flair kit a sticker proclaiming 'Fly with Flair' was included.

Geoff

[PatMc]

A flair is something a Scotsman stands on but the man from Laramie had one for ladies.

[PatMc]

Posted by Geoff Sleath on 01/12/2017 17:29:27:

The only full size aircraft I've landed are gliders. I was taught to flair when the height of a double-decker bus above the ground and just hold off gently but I guess a glider's pilot position is a lot lower than that of a 747

Geoff

When I was learning in T21's & T31's I would hold off the flare until I could distinguish the blades of grass !!!
My eyes were sharper then

[Dave Bran]

I realise this is a long while ago but a friend and I taught a Dan Air Pilot (on Comets) to fly models.

He could manage orientation APART from the landing, when he had to stand looking the way the plane was flying and look back over his shoulder.

I always worried about his passengers......................................

[Andy48]

Many years ago (well before 9/11!) I was invited to take a flight to Europe in the cockpit of a jumbo jet, sitting in the second engineer's seat which was not used on shorter flights. You certainly cannot see the ground as you land but you can see the runway approach. On this flight, there was a very low cloud base, and the pilots were in constant communication with each other and the control tower during the descent. Much of their time was spent adjusting the automatic pilot as they came down. Once out of the cloud, we were just a minute or two from touchdown and the plane was exactly on the white line in the middle of the runway. The pilot has said it was a short runway and they would need to use the taxiway whilst still braking. Therefore they landed very close to the edge of the runway. Difficult to say whether it was pilot skill or the automated control systems, probably a bit of both, but the pilots were certainly very busy during all of the approach and the landing.

These days the automated systems are much improved.

[Rob Ashley]

Hi Pat. Liked that one.....

[PatMc]

It was quite a long time ago, Rob.

In fact my gliding certificate book was signed by Brabazon of Tara, as president of the Royal Aero Club.

[Rob Ashley]

Nice!