Do we “bump down” these days? I was taught to land……

[Dogimed]

This was taken from another thread, quoting another user. But I was curious, How difficult is it to land a 737? or any 'large' commercial aircraft?

The landings always seem rough, but am told that particularly with the 737, you gotta put it on the runway quickly, without the need for a smooth touchdown?

Not a beat up, genuinly interested, are commercial pilots taught a smooth landing is important or does the plane need to be dropped onto the runway to keep it there?

Dog

[Dehavillanddriver]

i reckon the classic is easier to get a decent landing out of compared to the ng

[hoss]

I'm not too sure how they did it in the old days but there are the company stabilised approach requirements which can be 'policed' with the help of QAR's. Some one else may care to comment if they have noticed any changes in handling, speeds being flown etc. and has this had any impact on the apparent deterioration. For example the Dash seems to land so much nicer at Ref+10 and harder 'on speed', or maybe it's just me.

I can't speak for the 737 but I appreciate and comment if the bloke next to me flew the speeds, puts it firmly right on the 1000' marks and centerline of course:p . Anything else like 'mucking around' and floating looking for a greaser doesn't do it for me:rolleyes: .

Having said this, yes I'm guilty of bumping it on every now and then;) but when the greaser happens it feels fantastic knowing that I put it exactly where I wanted:) .

[Kaptin M]

I close my eyes from 100' above...after all, "Any one you walk away from, is a good one!"

These sorts of professional secrets are VERBOTEN, dogi...so don't believe ANYTHING you read!! :E

[triadic]

In my book, you get far more points for touching down on the nominated spot (eg 1000ft markers) than you do for a "greezer" somewhere else. If you can get both together - good one!

Most accidents occur on approach and landing and many the result of not flying a stable approach according to well established criteria (FSF etc).

Any move away from flying the right speeds etc or trying for a greezer whilst floating well past the 1500ft marks is only asking for trouble. And if the Rwy is wet, then a firmer touchdown is the go.

I seem to find many pilots these days that don't have the basic skills or self discipline to put it on the spot 100% of the time. Something to do with training I believe?

[Kaptin M]

...if the Rwy is wet, then a firmer touchdown is the go. Why?

[Wizofoz]

It avoids aquaplaning

[Kaptin M]

Oh really!!
And how does it do that?
Aquaplaning is a function of the square root of the tyre pressure, and will occur at an almost set speed on each aircraft type, regardless of how firm or otherwise the touchdown was, if there is sufficient standing water.....unless you figure you can make your "firm touchdown" at that speed.

[John Citizen]

If the runway is very long, much longer than "landing distance required", then I cannot see anything wrong in floating longer to make it a greaser, especially in an aircaft type difficult to "grease on".

Remember this very important fact :

The passengers (who keep the airline alive and pay our salary) can all feel the difference between a greaser and a thump,

but

the passengers got no absolute idea about touchdown zone markings etc,

Remember, some passengers are still very scared of flying and by making it a smooth flight followed by a smooth landing might encourage them to fly again one day or feel better about it.

[flyby_kiwi]

Ill go with John Citizen on that one,

If landing distance avaliable is not an issue Ill always make an effort to grease it on with pax. Admittedly in my applications however it concerns light piston a/c only.

[Wizofoz]

"Oh really!!
And how does it do that?
Aquaplaning is a function of the square root of the tyre pressure"

True when the entire weight of the aircraft is on the tyres. If a landing is "Greased" there is a period when the wheels are in contact with the runway, but the wings are still producing sufficient lift to support part of the weight. This has the same effect as a lower tyre pressure i.e. lower and wider range of speeds for aquaplaning.

Touching down firmly (a good idea at all times) puts all the load on the wheels and deploys the speed brakes in the shortest time, raising the the speed and shortening the range of possible aquaplaning.

By the way Kap,

How come you'll reply on this thread, but not on the one where you couldn't work out which decade an incident report was from?

[DirectAnywhere]

I'm not sure if it'll do much about aquaplaning - not that I'm saying it won't I just don't really know - but placing the aircraft firmly down in the TDZ will:

*minimise risk of a float and associated increase in landing distance
*correspondingly minimise the time taken to speedbrake deployment and ability to actuate reverse thrust
*by reducing time to full speedbrake deployment, maximise the weight on the wheels sooner and therefore increase braking effectiveness.

My two bob's worth.

[chief wiggum]

So if you want to make it a "greaser" then you have to "float down the runway" ?

If that is the argument, then why not aim for the 500' markers, float for 500' and "grease it on" at the 1000' markers ? surely this meets ALL requirements ?

Personally, my approach is to touch down on the 1000' markers AND try to grease it on. works most of the time, provided one remembers that Vref is the speed at which one should cross the threshold at 50' AGL, and not a touchdown speed!

[Antares]

You should be able to land smoothly AND touch down at the correct spot AND in a limiting crosswind, if you were trained correctly, and have some manipulative ability. IMHO the only pilots who advocate "firm" touchdowns are those who can't land properly or have no manipulative ability!
The training should have been done at abinitio, not on transition to heavy jets, as some think appropriate.:E

[Cloud Cutter]

In my opinion it is a foolish driver who puts 'greasing it on' ahead of precision. Sure you should aim for the spot AND try to minimise the thud - in that order. Wizofoz is quite correct, a positive touchdown minimises tendancy to aquaplane on a wet runway, further to that (I was told by an old pilot many years ago) drawing out the touchdown or greasing it on increases tyre ware (delamination) - not sure to what extent this is true these days (better tyres) but it makes sense, the sooner the wheels are doing the same speed as the aircraft, the less rubber you leave on the tarmac - anyone else care to comment on the validity of this. Points about spoiler deployment etc are also valid.

By the way, I'm not talking spine compressing 'arrivals', just a gentle, but positive touchdown - ask Boeing or Airbus how their aircraft were designed to be landed!:ok:

[tinpis]

FFS...a 737 is as difficult to land as a cherokee 6.

Whats the mystery?

[DirtyPierre]

Sure I'm not a pilot, but we were advised in good ol' ATC school - (I did the course at the now defunct Henty House, Melbourne) that weight of the vehicle had no bearing on aquaplane speed.

Aquaplane speed was a function of tyre pressure and speed, and that weight (or mass) of the vehicle had no effect. Hence, the advice to thump it down, because there was therefore more mass exerting force on the tyres would be incorrect.

We were also advised that to determine your aquaplane speed roughly (in mph), you take the square of your tyre pressure (in psi) and multply by 9. Hence if your tyre pressure is 25psi, your rough aquaplane speed is 45mph. Hence most cars will aquaplane at 80kph. I've managed to have it occur to me while driving through a large puddle at 90kph.

The reason we were advised about this using the old imperial measurements was because the film depicting the experimentation on aquaplaning was done by NASA. It showed a B1 thumping it down, then slowly drifting off the runway.

Tread pattern will make little difference, but grooves in the runway allow the surface water on the runway to drain quickly and help reduce the incidence of aquaplaning.

Correct me if I'm wrong, but I'm sure the info I received way back then is still correct.

[Dehavillanddriver]

Pierre,

you information is correct, but consider this...

the boeing documentation says that firm arrivals in the correct position are preferred over landing long and holding off for a greaser - tail strike being one consideration.

anyone who advocates landing long in order to get a greaser is on the wrong track in my opinion - but then I also disagree with Dash-8's landing long just because they can - it is most unprofessional in my opinion....

[Capt Claret]

DHD, does this mean you were not of the brigade who used to land (just) on 03 at Perth with a touchdown about abeam Delta? ;)

[flyboy6876]

I do notice the difference in the landings between a 737 and the 146. I've been doing a fair amount of commuting to Kal and Telfer over the last few months and the 737 landings always seem to be pretty positive, whereas the 146 just seems to trundle down onto the runway. Why is this?

But then again, sitting in the arse end of a 146 is a damn sight more uncomfortable (bouncy) than the 737 when cruising.:E

[DirtyPierre]

Dehavillanddriver,

I'm not certainly going to get into a debate about long, greaser, short and hot landings as this is outside my sphere of expertise (pity Dick Smith didn't do the same).

However, I must reiterate that weight of the vehicle has no effect on the aquaplaning speed, according to the experiments conducted by NASA. Whether the mass (weight) of your acft is partially supported by the lift of the wings, this should not affect the aquaplaning speed of the acft...according to the theory I was taught.

[Cloud Cutter]

DirtyPiere,

You are quite correct - this applies once the wheels have spun up, untill then you must take rotational inertia into account - it's quite simple, the greater the mass of each wheel, the more it will resist 'spinning-up', and of course, untill it has reached full rotational speed the tyre is by definition hydroplaning or aquaplaning (even on a dry rwy - it's called reverted rubber hydroplaning) - instead of getting caught up in the formulae, consider the basic physics. The extreme example of this effect would be landing with the park brake on - does that clear things up?

[DirtyPierre]

Cloud Cutter,

I'll take your word for the effect of rotational inertia. I think the formula might be just a rough guide you can use to calculate aquaplane speed mentally. It certainly works for cars, and it doesn't matter the weight of the vehicle, whether you're driving a Ford F350 or a Fiat Bambino.

[Cloud Cutter]

Please don't take my word for it, think about this - given your car example, that formula gives you a speed at which the car will hydroplane if you drive over a big enough puddle, if you put the anchors on, and give the wheels resistance to rotation, you can get the car to hydroplane at a much lower speed, particularly when your talking reverted rubber hydroplaning (when the surface of the tyre melts to form a liquid film) - this is essentialy a skid.

[Kaptin M]

but the wings are still producing sufficient lift to support part of the weight. This has the same effect as a lower tyre pressure i.e. lower and wider range of speeds for aquaplaning.Huh??? You've contradicted yourself if you re-read what you've written, Wiz, notwithstanding that weight has nothing to do with aquaplaning speed anyway! (The contradiction in your "hypothesis, is on the one hand you are stating that during the initial touchdown the lesser weight on the wheels "has the same effect as a lower tyre pressure", then you go on to say this equates to " lower and wider range of speeds for aquaplaning.".
My impression has always been that the speed at touchdown is faster than it is towards the end of the landing roll.
Do you know something the rest of us don't, Wiz??

Touching down firmly (a good idea at all times) puts all the load on the wheels and deploys the speed brakes in the shortest timeAs Cloud Cutter has pointed out, speedbrake deployment is dependant upon main wheel spin up.

DirtyPierre, the formula of 9 times the square root of the tyre pressure to give aquaplaning speed (in mph) was always the one I had used as well, but I seem to recall reading (somewhere) recently that there was now more of a range (something along the lines of 7-11) with 9 still the median.
Anyone else seen this reference?

Cloud Cutter, rubber reversion is the phenomenom that occurs when the water trapped between the wheels and the runway heats up (to form steam) and dissolves the rubber into smallish tacky "blobs", further reducing braking effectiveness through the tyre to pavement contact. Well that was my understanding of it, at least.

Anyway, avoid speeds around 80-90 kph in your car on days when it's p!ssing down - I experienced aquaplaning in my car several years ago (by not following my own advice :zzz: ) and ended up off the freeway in a gully. It's a strange sensation, you can turn the steering wheel full lock both ways with just an index finger, and NOTHING happens....I just kept going straight ahead foot off the accelerator, at the SAME speed (until I hit the grass) :ouch:

[cloudcover]

My belief of the theory has always been to do with
the efficiency of the wheel brakes i.e to get the weight
of the aircraft on the wheels asap (hence spoilers)

If the runway is wet, a greaser will not deliver the
true weight of the a/c but an apparant weight significantly
less which in turn will cause the wheels to lock-up and
engage the anti-skid system which will, due to less
braking efficiency will increase the landing roll.

If Im completely wrong..so be it! :O

[DJ737]

Put it on at 1000' whatever the conditions and if you stop / exit before the black stuff turns green, buy yourself a beer :p or better still get the FO to pay.

DJ737

The Roo Rooter :E :ok:

[404 Titan]

Kaptin M
speedbrake deployment is dependant upon main wheel spin up
Can’t see that that is one of the requirements for Ground Spoiler extension. Boeing might be different but the A330 FCOM 1 section 27 states that full extension of the Ground Spoilers will occur at landing if both main landing gear have touched down and:
· They are armed, and
· All thrust levers are at idle, or
· Reverse is selected on at least one engine (other engine at idle).

I have always been told that “greasing” it on is to be avoided, not because it increases the risk of aquaplaning but because it increases the risk of touching down outside the “zone”. If you know the runway is going to be slippery, it is best to get it on the ground, allow the spoilers to auto deploy and use full reverse thrust as these devises are most effective at higher speeds. Once the aircraft has slowed enough, the auto brakes with anti skid working should start to become effective. Obviously allowing the aircraft to float down the runway because you were after a “greaser” is a bad move in this situation and should be frowned upon.

[ActiveWilly]

It would appear that "bumping down" is still alive and well in a small town 300km to the east of Perth...

The local aviators (worried about avian flu these days I imagine) carefully "bumpdown" by the first or second wire on the runway... (oh, sorry, Rwy 10 doesnt have a cable arrester system, well what were you aiming for?)

Who needs a chiropractor after you have been shown a "bumpdown" reminiscent of Maverick in Top Gun (they all wear the glasses as well)... Even a chiropractor couldnt salvage what would be left of your spinal column...

It is rumoured that these pilots are so adept at "bumping down" that on many occasions they do this with such vigour that ones eyes retract in their sockets and end up somwhere around the anal region, hence the outlook achieved by many a young aviator in their employ...

If "bumping down" is an art, then they should all be bloody picasso... But then again, he put the one ear he had to good use...

[Cloud Cutter]

404

How do you think the aircraft decides the mains are on the ground? On all the Boeings I'm familiar with, an armed spoiler pops up automatically when one of the wheels (eg 727 right main) reaches a certain RPM - of course manual deployment can be done at any stage but is usually not the norm. Sounds like the 330 may be different, maybe olio extension - but then, who know's with Airbus (donning flack jacket):}

[hoss]

Kaptin M, I know what you mean about the differing formulae for calculating the aquaplaning speeds. Apparently it is 7.7 if the wheel is not 'spun-up' and 9 if it is:) .

[404 Titan]

Cloud Cutter

I haven’t flown the B747-400 or the B777 but I have just looked up the relevant section of their FCOM 1’s and nowhere does it refer to the wheels having to spin up before the Ground Spoilers deploy. Maybe it is just a B727 thing or something? It make far more sense to me to have the Ground Spoilers deploy on a squat switch or reverse thrust when you are aquaplaning than on tire spin up which make not occur until you are off the far end of the runway.

Ground Spoilers B747-400 (FCOM 1)
On the ground, the Speedbrake lever stop retracts allowing the Speedbrake lever to be moved fully aft to UP position. All six spoiler panels on each wing extend to their full travel positions.
When the Speedbrake lever is in ARMED position, thrust levers 1 and 3 are near the closed position, and the main landing gear touch down, the Speedbrake lever is driven to UP position, extending all spoiler panels. If the Speedbrake lever is in DN position with the main gear on the ground and thrust levers 1 and 3 near the closed position, and reverse thrust levers 2 or 4 are pulled up to idle detent, the Speedbrake lever is raised out of DN detent and driven to UP position. This provides an automatic ground spoiler function for RTO and provides a backup automatic ground spoiler function for landing when the Speedbrake lever is not armed during approach.

Spoiler Speedbrake Operation B777 (FCOM 1)
In the ARMED position, the speedbrake lever is driven aft to the UP position when the landing gear is fully on the ground (not tilted) and the thrust levers are at idle.
The EICAS memo message SPEEDBRAKE ARMED is displayed when the speedbrake lever is armed.

[amos2]

Hey!...do we really need all this bloody hi-tech mumbo jumbo?

Everybody with their bloody ego hang ups trying to out-ego every one else with their super duper mathematical formulas about how to land a bloody aeroplane with a bit of bloody water on the bloody runway!

For crying out loud!...just read the bloody Ops Manual!!!

It's all there, you silly bloody Donkeys!! ;)

[Wizofoz]

Kap,

Others (including yourself) with a greater understanding of this phenomina have made this a very educational thread. Thanks and I stand corrected on my misunderstanding.

This is known as admitting error-try it some time.

Amos,

If you have no interest in how Aeroplanes work, B***** off back to your fishing and but out of conversations between people who have something worthwhile to contribute.

[Dehavillanddriver]

Claret,

Yes I was the odd man out, and would land in the touchdown zone and taxi to the apron rather than hover taxi..

I was a big critic of the practice and was very disappointed that the check and training people in Perth actually encouraged it.

[max rate]

Um, Willy.........................that was Van Gogh!

[TheNightOwl]

It is more than two years since I left aviation, and I may be wrong, but I understood that, to have spoilers deploy automatically on touchdown of either Boeing OR Airbus, the following were necessary:

1. "Spoilers" lever to "ARMED"
2. "Weight-on-wheels" (squat) switch made
3. Both power levers at "Ground Idle" position

Spoilers will then deploy automatically, or have I got it wrong?

Kind regards,

TheNightOwl.

[turbantime]

Well, the way I see it....everyone that doesn't know anything about flying (ie most pax) will always judge the skill of the pilot by their landings. So, if they fly with company X and find their landings a bit "firm" and then fly with company Y who grease em on....me thinks that they'll think that these pilots are better and will wanna fly with them.

I've got friends outside the industry that live by this rule....the better the landing...the better the pilot...therefore I'm flying with them always!!!

So, if runway is available and weather conditions ok, then why not grease it on? In saying that though if it's raining or there's crosswind or on a short runway then by all means a positive touchdown is the saftest option.

My two cents worth anyway.

[Kaptin M]

"more than two tears since I left aviation" - Freudian slip there, TNO?

You are pretty much right - from the B737-400 Boeing manual

During landing, the auto speed brake system operates when these conditions occur:
- SPEED BRAKE lever is in the ARMED position
- SPEED BRAKE armed light is illuminated
- both thrust levers are retarded to idle
- main landing gear wheels spin up (more than 60 kts) - SPEED BRAKE LEVER automatically moves to the UP position, and the flight spoilers deploy
- right main landing gear strut compresses on touchdown, causing the mechanical linkage to open the ground spoiler bypass valve, and the ground spoilers deploy.

If a wheel spin-up is not detected, when the air/ground system senses ground mode, the SPEED BRAKE lever moves to the UP position, and all spoiler panels deploy automatically.

[Dogimed]

Umm, back on topic, (Surely you do more dry landings than wet anyway).....

If it is too hard to land decently, and you must dump it onto the runway.. surely you would need better training to land it decently on the right spot then? My dear old dad would never forgive me if i had that excuse doing circuits...

[Cloud Cutter]

Depends on your definition of decent landing. For me, it is getting as close as possible to what the aircraft flight manual says you should do.

[dogcharlietree]

1) Pax ALWAYS judge a pilot by his/her landings only.
Nothing else matters to them.
2) Friends of mine who constantly fly domestic in Oz are always commenting on the HARD landings these days. What has changed, they ask me. Ah.. I reply, the standard of the aviator!!!!
3) Aircraft with trailing link undercarriage (ie the one-four-sex whusper jet) by design allow for smoother landings.
4) The different aquaplanning speeds should be considered for landings and aborted takeoffs.
5) Some aircraft have spoiler deployment after main wheel spinup. ie Diesel 9.
6) Conditions in Oz (weather and runways) are almost always in our favour to conduct smooth landings (for RPT).
7) From my old friend AC Kermode (Mechanics of Flight) "The art of landing an aeroplane consists of bringing it in contact with the ground at the lowest possible vertical velocity and, at the same time, somewhere near the lowest possible horizontal velocity relative to the ground."
8) Ah, I'd like to see some of these so called pilots these days land a DC-3. I'd make a motza selling seats, for spectators, coz nobody would ride with them.

[404 Titan]

Some of you seem to be making the stupid mistake of rating the landing quality to determine the pilot’s skill. You should realize though that a large number of airlines, mine included, emphasize toughing down in the “Zone”, rather than a smooth landing. If you can achieve both then great, but certainly don’t go out of your way looking for it. As the pilot gets more experience on type he/she will be able to achieve it more often but ultimately conditions on the day will dictate the outcome to every landing, not just the skills of the pilot.

[Kaptin M]

IMO, you're quite correct, 404 Titan, after all isn't that part of what being a professional pilot is about.
The history pages are filled with pilots who tried to "grease it on" and eventually probably did. but ended up running out of runway and damaging the aeroplane.
As a matter of fact, I was just reading about an incident in the States where the Captain overran the runway, because he persisted in trying to land when he should have gone around ie. he touched down with insufficient runway length remaining. Not only did he not realise the aircraft limitations, but neither did the F/O (who should have told him to go-around).
The final words on the CVR transcript by the (52 y.o) Captain were, "Well, there goes my career".

I wonder if Bob Katter and Wayne Swan might have written him a letter of thanks for NOT going around, had they been on board at the time :rolleyes:

[NAMPS]

I saw the nicest landing in marginal wx at Coffs once.

It was a greaser...just happened to be on the old rwy 19 (turned taxiway). Pulled it up nicely too!

;)

[Dogimed]

Namps,

By these other philosophies, he/she must have been a very unprofessional pilot.

Kaptin M,

I'm not saying to risk life/career/plane.. just wanted to know if pilots were being taught that a good landing seems to show that the pilots aren't just sighing at the end of a flight and after all. IT IS what pax remember ...

404 Titan

Some of you seem to be making the stupid mistake of rating the landing quality to determine the pilot’s skill. You should realize though that a large number of airlines, mine included, emphasize toughing down in the “Zone”, rather than a smooth landing

You just answered my original question.

DCT
Someone told me recently

" A good landing is one you can walk away from, a great landing is when the aircraft can be reused."

Perhaps that is in the Ops manual?

Dog

[Wingnuts]

"Aquaplane speed is a function of tyre pressure and speed and weight has no effect ..... "

True, but pressure is dependent on tyre air volume which is dependent on tyre profile which is dependent on weight.

That is, the firmer the landing, the greater will be tyre distortion from max volume, 'round' profile. Hence the pressure will increase and aquaplane speed will be higher.

As the wheel spins up, centrifugal force will tend to restore the round profile and lower the aquaplane speed. How much depends on oleo pressure which depends on weight which depends on.......

--------------------

The bloke who ops for a greaser rather than a positive touch down on 'the spot', is generally the same bloke who does not have an issue with not using full runway length for takeoff.

[Dogimed]

The bloke who ops for a greaser rather than a positive touch down on 'the spot', is generally the same bloke who does not have an issue with not using full runway length for takeoff.

Why can't you greaser on 'the spot'????

Dog

[dogcharlietree]

C'mon Guys, We're not talking about the once-in-a-blue-moon 'greaser'. (which is probably around or less than 1in/sec).
I don't think the PAYING pax or us expect this unrealistic greaser.
All we want is an acceptable and bearable rate of descent when the flying machine contacts terra firma.
We are trying to workout why pilots these days test the vertical limit imposed by FAR's of 10ft/sec continuously.
There was an article that appeared in the flying magazines a few years ago which talked about the "Jacobson Flare", written by David Jacobson, a QF 737 training captain. Unfortunately I cannot find it on the 'net.

[Soulman]

Well, I can't say I fly a Triple 7 or a 73' (actually I fly VH-HXK - A Piper Warrior at Horsham) and while I might only have 8.6 hours flight time - I'm pleased to say that I'm learning how to land (at least better than my first few attempts!). Cut the power over the fence, glide, hold off, hold off, hold off, back pressure, back pressure, back pressure... Ahh, Got it down! And what's more, I'm on the centreline and have plenty of black stuff in front of me (and only a little behind me!)

Interesting thread - I love reading about how you guys in the majors do your thing - hopefully one day I can join in threads like this with the knowledge of an Airline Pilot. ;)

Cheers and wish me luck.

Soulman.

[amos2]

You stick with it Soulman and you will make the grade...after all, that's how we all started.

Now, back to the so called experts!...

Gimmee a break fella's, if you've been around the traps a few years, especially in airline ops, and you can't put it on smoothly more times than not,then God help us all!!

I could do it, why can't you?

[Chimbu chuckles]

Soulman that's great in a Piper but try it in a jet and you'll;

1/. Smash the tail on the ground, or

2/. Drop 140 tons of aircraft in from several feet up...making the 'bumping down' landings discussed here look like greasers!!

The main undercarriage in a jet is almost always (edit: a long way) behind the axis around which the aircraft pitches...hence if you keep pulling back 'for a greaser' the opposite will result, you'll drive the wheels into the runway...presuming you don't bash the tail on the ground doing millions of $ of damage first.

You can get nice landings that impress the punters but that is not the imperative. You must land in the defined touchdown zone OR ELSE!!!

When you land a jet you, most often, fly an ILS and then when the talking radalt says 50' gently pitch up a few degrees, to arrest the rate of descent, and when you hear 20' gently reduce thrust and just let it land...timed right you get an 'acceptable' landing...it's all in the timing. To get a more consistant 'really nice' landing you can gently reduce back pressure (after the pitch up) to 'lift' the rear wheels enough to further cushion the touchdown...often, if done right, earning yourself a greaser...but not always.

In some conditions the most professional thing to do is just 'put it down' in the right place!!!

Now to the matter of 'wet runway' techniques.

The most abused/missunderstood technique is this thing about slamming an aircraft on the ground on 'wet' runways....it's a STANDING WATER technique NOT A WET RUNWAY ONE!!!!!

The number of dickheads, including senior captain/check captain dickheads, I've seen prolapse every heamoroid on the aircraft because a runway is 'wet' is truly amazing.

It's for landing on up to 1/2 inch of standing water...not bitumen discoloured by rain...even steady rain. Given most big runways are grooved is even less reason to ever have to drive an aircraft on using a technique designed to drive the wheels down through deep water to get to the actual runway!!!

Hands up any airline pilots who have an ops manual that allowes operations in standing water/innundated runways??

Chuck

[flyboy6876]

You mean sort of like this Dogimed?

Not a Piper, but a jet (http://www.rits.net.au/download/MD-80.mp2)

[DirectAnywhere]

The main undercarriage in a jet is almost always behind the axis around which the aircraft pitches

Chimbu, I would hope so! Given that an aircraft pitches about its lateral axis which runs through the CoG, if the CoG was aft of the main wheels the aircraft would sit on its tail on the ground. I think the main wheels on ANY aircraft that's correctly loaded are aft of the CoG. The longer moment arm between the CoG and the main wheels on a jet leads to the problem you've described, not the fact the CoG is ahead of the wheels.

[Wingnuts]

Dog

To grease it on, your sink rate has to be minimum. Or you can 'roll' it on a la 727 so that the mains are going up as the aircraft hits the deck. You risk a very firm landing if you are too late and float if you are too early. Only recommended for the aces.

Another way to arrest sink is with a spurt of power, again not recommended as it increases fwd momentum, speed, fuel, brakes and distance. Or duck below approach angle and level out prior to touch down on 'the spot'. Risk is landing short (unexpected sheer, power loss) and approach obstacle clearance but in both cases, the pax will be impressed.

But it depends on the aircraft, wingloading etc. The 747 will grease it on almost every time because of cushing ground effect as will the 146 because of very forgiving gear geometry.

[Dogimed]

Woomera? Moving it here has killed the thread.

Dog
:{
Ho hum...

[Bevan666]

I think what Chimbu Chuckles is trying to say is on a bigger aircraft, with the main wheels behind the CoG a small change in attitude will produce a significant movement in the position of the main wheels.

In smaller aircraft, a 1 degree pitch change might move the wheels up and down by an inch or so, while on a larger aircraft this will be a number of feet.

This is all due to the distance from the CoG to the main wheels.


Bevan..

[DirectAnywhere]

Agreed. But the point I'm making is that Chimbu stated the main wheels are ALMOST always aft of the CoG in a JET.

The main wheels are ALWAYS aft of the CoG in any aircraft. As I stated (maybe re-read my original post?), the moment arm, ie. the distance between the wheels and the CoG is what makes the difference, not the fact that the main wheels are "almost always" behind the CoG.

[hoss]

"the main wheels are ALWAYS aft of the CoG in any aircraft"

Try telling that to the DC-3 guys out at Bankstown:ouch: :ok: .

:)

[DirectAnywhere]

Ooopsss...in any tricycle undercarriage aircraft. Ta!!!:\

[Chimbu chuckles]

Sorry guys....what I had intended to say was that the main undercarriage of a jet aircraft is almost always a long way behind the lateral axis.

As opposed to small aircraft where you can keep pulling to get a touchdown as slow and gentle as possible....that's a recipe for disaster in a jet, particularly a large one.

Chuck.

[flyby_kiwi]

Its all a matter of perspective,

If im landing a B737 at MLW on a 1300m runway - Id be looking at putting it on the spot, unfortunatley for myself its more likley to be a C172 landing on that 1300m runway so Ill be going for the 'greaser' from a 6inch/min decent rate in the hope the pax. will like it and Ill get a tip so that I can afford to eat that night. :ok:

[ROB-x38]

I've heard a comparison between landing styles:

"Light aircraft are stalled on, airliners are flown on"

Don't know if i subscribe to the theory just throwin it into the mix :uhoh:

[DirectAnywhere]

Chimbu Chuckles...agreed!!!:D