Too easy to makes greasers? Questions on the ground effect

[vololiberista 205]

Didn't know that about the Victor, I have 5 books about the Victor, including articels about the Victor written by A.H. Fraser-Mitchell but never noticed this detail.

It was fairly early in the orginal design stage. But interesting nevertheless that winglet aerodynamics that we see on almost every aeroplane today were being considered in the 50's.

[scandinavian13 5,192]

Full names in the forum, please.

[G550flyer 1,013]

 

 

Should you be fully aligned with the runway before touch down or your are allowed to decrab a bit after touch down

I'm addicted to the decrab on very short final. It's been beat into my head for years during my AirForce days. Some where between 300ft and 100ft I go wing low. I like it because it gives me a feel of how much rudder and aileron I need to keep her pointed straight down the runway. Also gives me a moment to warm up my hands. As Polizei pointed out, touching down in a crab can be an jolting experience for passengers. Odd feeling you get as the plane snaps in alignment and suddenly feel the pilot kick the rudder.  Unfortunately, some aircraft don't behave as expected in flight sim.

[Chock 17,769]

The 747's undercarriage was designed to be able to handle touching down in a significant crab - as was the B-52's  - because it was thought that, with that big wingspan, those types would have a significant chance of striking (or in the case of the B52) overstressing a wingtip on touchdown. In fact the B-52, goes the extra mile in that regard, in that it has swivelling landing gear specifically designed to allow it to land at crabbed angle.

 

Ensuring those big aircraft can handle a bit of sideways force on the landing gear at touchdown means there is less chance of a pilot worrying about making sure the wheels are perfectly aligned straight rather than concentrating on avoiding the risk of a wingtip or engine pod strike, although theoretically at least, you should kick out any crab angle just before touchdown.

 

If you do a search online, you'll find plenty of videos of 747s doing crosswind landings where they touchdown at some very odd angles and end up none the worse for wear. Here's one at Kai Tak:

 

https://www.youtube.com/watch?v=OtnL4KYVtDE

[thibodba57 462]

Get used to landing with the crab. When the -8 comes out you don't want to dragging wing low.

[Werner747 107]

Without doubt the 747 is the best aircraft ever built and is a real pilots machine. It is very manoeuvrable and forgiving given it's size. I have spent many a pleasant hour flying the old girl both the -200 and -400 derivatives. It has a reputation for being an easy aircraft to land.

A good approach generally leads to a good landing (as always there are exceptions) so get this part right to help make your landings easier.

 

In the early days most jet aircraft were configured in the landing configuration by the outer marker and flew the whole final approach at VREF+ an additive. As fuel became more expensive airlines adopted low drag approach techniques which consisted of delaying selection of both the landing gear down and the landing flap position. Typically the landing gear is lowered anywhere from 2000 to 1000 ft and the engines spooled up in the landing configuration by 1000 to 500 ft. However an undesirable consequence of this technique (and step down non ILS approaches) is the increased risk of either high descent rates developing and or high landing speeds, usually with engines unspooled, or at very low thrust settings. In an effort to reduce the number of landing incidents (runway under and overruns) most airlines have adopted a stabilised approach policy. This is whereby the aircraft must be configured in the landing configuration, on speed, spooled up and with a normal rate of descent by either 1000 or 500ft above aerodrome level or else a mandatory go-around is carried out. This point in space is referred to as "the stable gate" and typical criteria for a wide-body would be:

• established on correct glidepath
• Airspeed +10 or -5kts of target speed (TTS)
• Sink rate <1000fpm - or if going to be higher then brief for it beforehand ie. non normal landing config.
• thrust appropriate (not idle)

To help achieve this an airline may implement configuration requirements such as (wide body):

• Gear selected down by 2000 ft AAL (above aerodrome level)
• Landing config established by 1000ft AAL
• Stable by 1000ft AAL or GA

These would be good to aim for in your own flying. This now places us on slope, on speed and hopefully in trim. If you are then you shouldn't really need to adjust the trim. All we have to do now is enjoy the ride.

 

Your final approach speed (TTS - Threshold target speed) can be determined by adding 1/2 of the steady headwind component plus all of the gust factor up to a maximum of 20 kts and a minimum of 5 kts. So for example if we were landing on Rwy 36 with a wind of 060/20 G35 the headwind component would be 10 kts and the gust factor 15 knots.

In this case our additive would be 10/2 + 15 = 20. If on an autoland just use 5 kts as the Autothrottles remain engaged.

 

From the corner of your eye monitor the thrust setting and if you see it start to increase signifcantly from the norm then check forward and the opposite if thrust reduces by easing back. This changing thrust setting could be due to something like "chasing" the GS or encountering a gust or shear and is to preempt the resultant pitch change that will occur with thrust changes. This is due to the pitching moment produced by big underslung engines. If you where already on speed then resist the temptation to trim as you will hopefully soon be through the area of shear or be back on slope. Remember the pitch, power speed/trim relationship.

 

Fly the electronic glideslope in preference to the VASI or PAPI when on an ILS. In large aircraft they will guide you to different aiming points. Fly the visual slope indicator if on a non ILS approach. This is of course in the RW and may have limitations when applied in flight sim as it depends on how accurately the scenery developer placed the GS and VS aids. This difference in aiming points is due to the difference in height between the GS antenna height (ILS) and the pilots eye height (VASIS or PAPI) and minimum landing gear clearances crossing the threshold. If you look at any runway that is utilised by large aircraft you will notice that the visual slope aid is positioned further down the runway than the GS antenna. Visual slope aids are always positioned abeam the aimpoints (the big blocks) marked on the runway.

 

If on an ILS aim to land between the second and third markings (300m to 450m) and go-around at the last set or 1/3 of the way into the runway whichever is less.

If following a VASIS or PAPI, as you would following a Non - ILS approach, then then follow it and aim for the large blocks. Of course this all assumes that the markings have been done correctly by the developer.

 

 

As I teach it to new crew learning large aircraft landing techniques:

• At 100ft "wake up" and 50ft "look up". In fact for the 747 as the nose crosses the threshold and it passes behind will do. (Disconnect the auttothrottle at the 50ft call unless on an autoland)

  At that point look to the far end of the runway. This will assist with the flare.

• At the 30 ft call ease back on the yoke to arrest the rate of descent (only 2 to 3 degrees pitch up - but don't look at the ADI)

  Hold the attitude making only small corrections if required to maintain descent rate and retard the thrust levers to idle (pitch up first then retard - especially when heavy). Thrust levers should be at idle by touchdown.

• Hold sufficient back pressure to maintain the attitude. Do NOT trim in the flare.

  Let it settle on. Flare times can be from 4 to 8 seconds in duration.

• The attitude on touchdown should be between 4 and 5 degrees. (you could perhaps look at this during a playback to check).
• After touchdown don't just release the yoke but initially hold the attitude, select reverse thrust and then lower the nose and fly the nose wheel onto the runway.

I find that landing a light 747 I would start the flare between 30 and 20 ft. After a while the rate of change of the radio altitude call outs will give you a clue as to runway closure rate.

 

2 things generally will lead to a poor touchdown.

• Unstable approach
• Not looking at the far end of the runway from 50 ft and during the flare.

Happy landings guys.

Thanks for the information!   It answered a few questions I had and following your directions I pulled off a -75 ft/s landing at MMGL last night!   I enjoy the landing dynamics of the Queen but armed with some new techniques now, it should go even better!

 

Regards

[scandinavian13 5,192]

Finding it massively ironic that a guy with the name 'polizei' ("police" in German, for the non-German speakers) cannot comply with forum rules.

 

 

 

Again - reminder: sign your posts - first and last - or they disappear.

[kevinh 409]

While the 747-400 can certainly land crabbed the autopilot reduces the crab angle at 500 feet using sideslip and lands upwind wing low. So it's a combination of crabbed and wing low.

[Captain Kevin 586]

This is why. Been a rule since 1999.

 

http://www.avsim.com/topic/245586-you-must-sign-your-full-real-name-to-posts-to-use-this-forum-posts-without-names-will-be-deleted/

[scandinavian13 5,192]

Kevin,

 

Just noticed that your signature does not include your real name, per the forum rules. Please fix this.

[Captain Kevin 586]

Kevin,

 

Just noticed that your signature does not include your real name, per the forum rules. Please fix this.

As a matter of fact, it actually does, look under the banner, you'll see it. May have to look hard, but it's there.

[scandinavian13 5,192]

Signatures, guys.

 

Final warning.

 

Sign posts, or they get removed...this is especially the case when a thread has drifted so far off the point that we're debating the minutia of various SOPs, and dragging in unrelated aircraft.

 

Please don't make my job more difficult.

[serviceceiling 135]

Well, to get back to the topic: I always have an external landing rate monitor program on (ProjectFly tools) and even a landing that might seem like a greaser in the sim can in fact be a -200 to -300 fpm touchdown, which in airplanes like a Q400 or A320 is a tad harsh. I think the 747's landing gear just absorbs shock pretty well and makes even a standard rate landing seem like a greaser. Nevertheless the 747 is pretty easy to hand fly on the approach, it's stable, flares pretty well and is far less slippery than a 737NG or 777 on the glide.

[Werner747 107]

Well, to get back to the topic: I always have an external landing rate monitor program on (ProjectFly tools) and even a landing that might seem like a greaser in the sim can in fact be a -200 to -300 fpm touchdown, which in airplanes like a Q400 or A320 is a tad harsh. I think the 747's landing gear just absorbs shock pretty well and makes even a standard rate landing seem like a greaser. Nevertheless the 747 is pretty easy to hand fly on the approach, it's stable, flares pretty well and is far less slippery than a 737NG or 777 on the glide.

Yes but our VA uses the ACARS system - I can always see what I am landing at and last night on a flight from MMMX-KORD I pulled of a -34 feet per minute landing so the technique works :-).   I do occasionally get the odd 150+ fpm landing but they are rare if you follow good procedure and technique.

 

Regards

[scandinavian13 5,192]

If you're concentrating on landing rate, you're concentrating on the wrong metric.