Landing
 

Hi folks, I am not a pilot in any capacity but an avid aviation lover (and Aero engineering student) and I was wondering. From my hours of geeking it out on YouTube watching videos of all sorts of aircraft I noticed something. On landing, commercial jets seem to aim for a point some distance down the runway but he military jets seem to always land pretty much on the numbers. Any particular reason for this or is it just a trivial observation?

Thanks for your time.

Well, I'll start the answers, although it's been a while. A commercial jet is operating to Performance Category A, which sets out all sorts of figures to achieve the safe flight. On approach the aircraft is assumed to cross the runway threshold at 50' at Vref (approach reference speed), with the speed reducing at a rate of 1kt/sec, and aiming for a touchdown within the touchdown zone markers (the big white markers some way beyond the threshold). This allows adequate margins for both stopping and going around. Military jets don't operate to the same regulations; I'm sure someone will come on soon and explain their side of things. I'm equally sure someone will correct my explanation, but it's a starting point.

Land on the numbers, Bloggs!

Duncs:ok:

On top of Herod's points, mil jets generally fly visually judged approaches, for which the piano keys/numbers form the most obvious aiming point, whereas commercial aircraft will more often fly a radar or internal aids approach, which will bring them down between/next to the PAPIs/VASIs rather than on the threshold.

And commercial flights rarely go around, whereas a mil jet doing a touch-and-go will want to get on the ground soonest to leave the maximum amount of runway for the subsequent take-off.

And mil jets are more manoeuvrable than airliners, so there's a better chance of correcting an approach to the threshold if it becomes apparent that the aircraft is going to undershoot (no guarantee though, as the fence along the A15 at Waddington will confirm...).

In addition, virtually all Civ-jets have thrust reversers on their engines, which allow the engines to help slow the aircraft down faster, and thus can stop in pretty short order. They simply don't need as much runway to stop that way.

The only tactical military jet I know of with a thrust reverser is/was the Saab Viggen... thus they need more runway in which to slow their faster-landing-speed jet via their wheel brakes.

Mil-jet transports do have thrust reversers... and so tend to land like airliners.

Civilian airfields are built to maximise revenue, hence the huge shopping mall with attached aircraft-parking facilities, along with a consideration for safe operations; i.e. it doesn't do to frighten the punters, or they'll go elsewhere for their cheap booze and crap tan.

Military airfields are built down to a 'cost', usually at tax-payers expense, and therefore less is available to be spent on concrete and Tarmac.

However, I should like to point-out that I always preferred to stop, and subsequently land, as opposed to land, and then try to stop.

The instrument touch down zone is 1500ft from the threshold, which allows for safe threshold crossing heights for large jets - which will also fly visual conversions to the same reference.

The point-and-power technique for light aircraft requires a nominated touchdown point and also some flex to allow for loss of power - so a typical RAF primary trainer flies about a 4.4° approach rather than a 3° approach (yes they do, do the mathematical calculations if you don't believe me!).

The higher approach speed and flatter approach paths of most fast jet aircraft require the sky gods, masters of their craft, to land as close to the runway threshold as is acceptably safe.

tactical military jet I know of with a thrust reverser?
 

Try a Tornado, rather natty installation I always thought...

The mighty Tornado also has thrust reversers!

Some civvy pilots aren't good enough to put it on the numbers without f-ing up. The policies have to fit the worst guy qualified.

It's a trade off. Do you hit the numbers or the piano keys? If you land a bit long on most landings, it won't matter much. If you land a bit short it will almost always matter.
Certain aircraft types like harriers, or bush pilots doing strip landings will always try and hit as close as they can the end of the runway. Many other mil types may need to land close to the edge in case of wartime bomb damage, and day one of the war is no time to start learning.

What if the numbers are in the piano keys?

SGC

Then there must have been a very good party at the airfield the night before....

Guys, thanks for all of the info, I appreciate all of your time. Just 2 weeks into my Aero Engineering course and already had one lecture on the Typhoon and another on the Tornado (and agree, it does have reverse thrusters) so absolutely loving it.

Thanks again!

I'm sure someone (oh alright, me then) will mention landing an F6 Hunter on a wet Chivenor runway in calm wind. Brick one was preferred, with the power already slipping to idle; then parking brake on (probably not QFI endorsed) and let the Maxarets do the work.
Also Gibraltar - esp in 240/25.

Landing
 

Civilian aircraft are not supposed to land on the threshold (piano keys/numbers or whatever). They are supposed to cross it at 50ft, end off.

One reason military jets land accurately on the "spot" is that they don't care much about finesse (a 2g landing felt by one person is not the same as felt by 300 passengers!). There is also more limiting landing performance as alluded before, so they trade finesse for accuracy.

Are you saying my landings lacked finesse?


OK, fair cop, everybody else did.

I generally use the grass next to the paved runway either just beyond the PAPIs or right at the beginning of the gable markers. This allows a shorter (relative) ground roll in order to reload and get back into the air with the shortest turn around. Horses for courses.

Try landing on the numbers in a heavy jet and you can expect to leave most of your landing gear a good distance behind you.


In civilian flying you are required to stay on the glideslope and /or Vasi until touchdown.


What you do in a Tornado is irrelevant :E

Whilst a Nimrod might not have been a 'heavy' jet, there was certainly no need to touch down 1500' from the start of the runway; particularly when carrying out a visual approach. Landing performance allows for the ac to cross the threshold at 50', at VATmax with an average pilot etc and have stopped before the end of the tarmac and, if conducting an instrument approach, changes to the approach path in the final stages would be ill advised; however, if you are looking out the window (and remember where the wheels actually are) you can land an aircraft where you want - preferably not in the undershoot. Landing 1500' in does not imply a smooth landing; neither does landing on the numbers imply 2'g'. I've landed smoothly on the threshold - once, I think - and thumped it in beyond the instrument touchdown point plenty of times - it was sometimes required to wake up the AEO!

Duncs:ok:

Slight deviation from the original question, but why are Ryanair landings the roughest you'll ever encounter? (of course there are exceptions)