747 Landing technique

[Dave]

For the final approach say from 1000ft down to say 100ft, what technique is used on the 747?

Is it the "point and power" technique whereby Pitch attitude controls rate of descent and Power controls speed...... OR.....

Is it the other technique (don't know the name) whereby Pitch controls speed and Power controls rate of descent?

Thanks.

[SMOC]

No 1, aim at the aim point and control speed with power.

[wiggy]

Yikes, that question brings back memories of pounding the circuit at CFS, and many happy "flarepath" demos and the like.... .........


Anyhow pitch/roll controls the aim point, power for speed.

[OSCAR YANKEE]

Suppose it all depends on where you come from....

Where I come from power controls your ROD (or ROC for that matter via excess thrust) and pitch your speed.....

Then again on airliners, it all seems to be a bit of a blur cause of the FD and autothrust, in my experience.

But Raw data, manual flying, manual thrust.....pitch for speed and power for ROD for me.....;)

[Port Strobe]

Maybe they're all linked?

[Justin Cyder-Belvoir]

At GS intercept select the attitude for the 3 degree descent and reduce the thrust to give you the correct ROD. The attitude controls the speed and the thrust the ROD. Increase the thrust and to maintain the correct airspeed make a small attitude adjustment hence the ROD will reduce.

From DH to touchdown it reverses: the control column manages the flight path and the thrust the speed.

SO the answer is both :{

[wiggy]

AFAIR it many Moons ago in some "decending" exercises on the JP ( basic Jet) we taught power controls ROD and attitude controls airspeed, (Oscar Yankee's point) ...and that was the technique to be applied at medium level and was also the one to be used around the finals turn - e.g if you were low half way round finals you applied power to reduce ROD and raised the noise to control speed.

However once rolled out on finals the teaching was to point at the numbers and control speed with power. There was a bit of angst and discussion at times about teaching Blogs this apparent change in technique but at the end of the day as long as you realise pitch / power is interrelated, as we all know, then I guess we use whatever "method" works for us.

Frankly I reckon you are stuffed if you end up thinking too much about it - then again you should see/feel some of my landings on the 744 :ooh:

[Intruder]

Power + Pitch = Performance. Trim the pitch to hold the speed and set the power to maintain the descent rate. Adjust both as necessary.

If you're having to consciously think about "technique" such as this on final, maybe you shouldn't be flying a 747!

[Junkflyer]

I agree Intruder. Don't really think about it just do it. The classic seems to like abut a 3 degree pitch on a 3 degree glideslope at 25 flap. If you are flying a higher pitch to hold glideslope, just add 5 knots and vice versa.

[GlueBall]

If you watch the autoland at work you will note that the autothrottle [thrust levers] movements always correspond to airspeed variations, and elevator for pitch.

[point8six]

Intruder says it all. For a constant angle final approach in still air conditions, you need a combination of power and pitch - get it right early on and you won't need to vary either, but remember that an increase in power will result in an increase in pitch and vice-versa. After a few attempts on the simulator, it will become secon-nature.
Glueball is quite correct in the demonstration of an autoland.

[DGAC]

To achieve the correct glidepath/glide-angle, pitch controls speed and power controls rate of descent.

Once on the correct glidepath/glide angle, power controls speed and pitch/bank points you at the landing point.

[Bula]

hhhmmm.. power for RoD.... something about swept wing jets and the aerodynamics of the drag curve which makes me cringe at the idea, BUt each to their own. You tend to use both anyway, simultaneously!

To fast pitch up, higher rate of descent, more power, still to past pitch up, even higher rate of decent, more power etc etc etc. :sad: I feel for the people down the back.

[jpu0509]

Trim, then pitch 4 speed, power for RoD works until I screw something else up!

[mustafagander]

Talk about dead men walking!! :eek:

Swept wing jets ALWAYS require pitch for aiming point and thrust for speed when on approach.

End of story. :ugh:

[captainsmiffy]

Gentlemen (and ladies)

Am surprised by your confusion. On a light aeroplane without much in the way of excess power and certainly very little inertia then the favoured technique was always to control the speed with pitch and the rate of descent with power. I was taught this in the airforce and taught it myself. Can you imagine, however, just how uncomfortable this would be to your pax in the back of a highly powered and heavy (ie loads of inertia) widebody jet?! Remember, inertia is the reluctance of a body to change, in this case, its speed and would need a pretty impressive pitch change to achieve this effectively in, say, a 200 ton aeroplane. We all, probably instinctively, point at the aiming point and use thrust to achieve the desired speed on anything from a turboprop upwards. It is just that you have 'forgotten' that you do it and you do it instinctively. It is also true that power and pitch are totally inter-dependant so that,although both methods work out, only the thrust equals speed and pitch equals descent rate is the really appropriate method to use for large inertia aeroplanes.

I'll standby for some flak.....

[mark sicknote]

I fly nothing bigger than a 172 and to be honest I have never really thought too much about this until now. On final I make pitch and power corrections without consciously thinking about it. in fact, after contemplating this thread, I'm afraid I'll over think my next approach and bugger it up!

But then this was a 747 thread...I'll get my coat.

[jpu0509]

I just kinda do it, landing that is.:ouch:

[Centaurus]

Crosswind landings in a 747 or similar heavy jet. The inertia of these types must cause a handling problem to pilots learning to handle crosswind landings.
Assuming the flare manoeuvre to touch-down is 3-5 seconds it means you have less than that time to "kick-off" drift (I know that is a wrong term but you know what I am getting at presumably) to ensure the aircraft touches down aligned with the runway centre-line - ie nil drift angle. With such a large mass is it normal therefore to keep the thrust up for as long as it takes for the nose to swing around in alignment, and then close the thrust levers after touch-down?

The crosswind landing technique is probably the same on a 747 or similar wide body as a B737 right down to a Cessna 172. Of course the inertia of the 172 makes it easy to align with the runway with a touch of rudder during the flare. But I guess it takes several seconds to align a 747 with the centre line assuming sat max crosswind angle. I have not flown a 747 which is why I am curious as to the time in seconds needed to complete the alignment procedure to nil drift.

[FullWings]

...The pitch axis is ahead of the main gear, so as you descend to last 5', the mains pivot away from the asphalt (relative to the fus)...

This technique has been talked about quite a bit but when you work out how much you move the wheels in the vertical plane by doing this, it comes out as inches over a few seconds: not likely to make much difference. I think what might be happening is that you are touching down at a lower pitch attitude, so when the ground spoilers deploy there is less of a change in lift and not as much for the oleos to absorb all in one go; also, by the time the GS do deploy, most of the travel has been used up. Watching aircraft land from the holding point, you often see what appears to be a perfect touchdown spoilt by spoiler deployment as the plane sits down on the bumpstops...

My theory is that in many aircraft, the smoothest landings result from having a certain (low) rate-of-descent when you touch down, which is progressively removed as you sink down on the suspension, leaving the airframe at rest in the normal axis w.r.t. the ground and at the 'taxiing' level of extension on the oleos. :8

[overstress]

The crosswind landing technique is probably the same on a 747 or similar wide body as a B737

Nowhere near. :cool:

The 747 has its own special problems due to the configuration, ie wingsweep and pod ground clearance. On a 737, get to just above runway, chop power, both hands on wheel, wrestle it to the ground, don't worry about bank too much. On a 747, gradually reduce thrust in flare until levers reach idle stops at touchdown, simultaneously remove drift with rudder and maintain absolute wings level with wheel. More than 6 degrees of bank at this satge and you'll scrape a pod. The outer portion of the wings with engines 1 & 4 flexes downwards at touchdown as the lift comes off the wing, reducing the ground clearance.

If you try and land a 747 like a 737 you'll scrape metal. :ooh:

[Meikleour]

This old chestnut just runs and runs ..........

Since most initial flight training starts on single engined aircraft, the forced landing technique requires that pitch for speed control be taught (ie. no engine available) however, moving on, with multi and jet aircraft, a combination of techniques is subconsciously employed whereby the pilot is generally using the same technique as the autoflight systems.

[misd-agin]

Nothing like watching a developing sink rate....and the only response is power.... if you're high enough it will work, if you're not high enough :uhoh:

[Trent 972]

This is one for all the 'Pitch for Speed, Power for Rate of Altitude change', (in a swept wing podded engine jet, ie. 747 ) brigade.
Sit at the end of a runway in a 747, pull the column back to make it accelerate down the runway and bring the thrust up out of idle to make it climb away.
When you can do that, I'll be a believer.

[RVF750]

Sweet. Says it all.

The problem for folk is that in essence, it's not easy to prove that the same controls in every aircraft do the same thing. Houses smaller, houses bigger, etc. I used to teach power for speed from the start as it was more logical, but also show the other method when one of the variables was fixed. Works for forced landings and jammed elevators too- I also used to teach both methods of PFLs too and let the student choose which fitted their mental model..

B744 or C152, they're all aeroplanes (didn't mention Airbus there though:oh:)

[Graybeard]

TK951 with its closed throttles and trimming pitch for altitude to stay on GS didn't work out so good. If the pitch trim had been used for speed instead of altitude, the closed throttles would have made it sink below GS sooner, and given the pilots, "Too Low, Glideslope" in time to make a recovery with the trim properly set for the speed.

Cute, Trent, but until it's planing through the air, it's not an airplane.

[galaxy flyer]

Except for FBW Airbus, planes are trimmed for a speed, not an altitude. Flying along straight and level at 250 KIAS, ADD power to increase speed--what happens? The plane, whether a C150 or a B747, begins to climb in an attempt to maintain its trimmed speed. Pull back the throttles and it will descend.

Power + Attitude = Performance

Trent OK, trimmed for take-off, pour on the coals, what will happen at about V2? It should, discounting any negative angle of incidence, lift-off and try to maintain V2. Why didn't it lift off right away, you say. Because it hadn't reached its trimmed speed.

Airbus FBW is G-stable, not Speed-stable, so pitch controls speed doesn't apply. Please refer to M. DesCartes for reasons why they did that.

[Capn Bloggs]

For captains: Always remember and forever take heed; left hand for glidepath and right hand for speed!

Primary effects of controls apply.

Do what the autoflight does. If you get slow, put the power up (counter the underslung-pitchup if necessary). If you get high, stuff the nose down! As mentioned earlier by Unhooked, try staying on the glideslope of an ILS with the power and controlling speed with the stick. Entertainment-plus.

The reverse works in a C150 only because of the powerful secondary effect of controls.

Flying along straight and level at 250 KIAS, ADD power to increase speed--what happens? The plane, whether a C150 or a B747, begins to climb in an attempt to maintain its trimmed speed. Pull back the throttles and it will descend.
True, but that's the secondary effect of controls eventually working. On final, we don't have time to wait. High? Stuff the nose down and then pull the power off a bit, anticipating the secondary effect of controls (push nose down, speed will eventually increase).

[galaxy flyer]

Cap'n Bloggs

Congratulations on the 3000th post, but

I do not aspire to fly like an autopilot, I trust you don't, either. My observations are based on a 1000 hours of T-Gs and approaches with students in the Galaxy, and another 10,000 in everything from the C-150 to the Galaxy.

Truth be told, it is hard to separate the two actions. If high, pulling off the power will require pushing the nose over and vice versa. But, we trim for airspeed and not for altitude.

GF

[Capn Bloggs]

Congratulations on the 3000th post
Yikes...! :{