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RUDAS
30th Oct 2004, 13:11
Hi guys.

I was just wondering if anyone has any contributions to make regarding the best technique of landing a new,very clean airframe C172R on short,grass strips.

i am based out of a large airport,and have surprisingly little experience on the latest 172s on short grass strips,having flown many hours in older ones,which have flap 40 deg and are generally much 'dirtier' airframes,so the 172R seems to float forever...a problem if you're heading for a ravine at the rwy end and still haven't touched down...:{

thanks:ok:

Say again s l o w l y
30th Oct 2004, 13:39
A fairly simple one, get the speed right!! 60 to 65-ish knots is plenty quick enough. The vast majority of problems with landing are down to speed control, slow it down to remove some energy and it'll probably be fine.

RUDAS
30th Oct 2004, 14:16
yeah,in fact its quite odd-i get it down to 55 kias and it still floats-flaps 30 (max).was wondering if taking about 5 deg of flap AWAY as i enter the flare might help????

Flyin'Dutch'
30th Oct 2004, 14:40
Only if you want to slam dunk it on.

I haven't got a 172R POH to hand but what I normally do when I fly a new type is to take it up to a sensible altitude and configure into landing set up.

Do few stalls like that. Note stall speed. Multiply by 1.3 and you have now the correct approach speed for your aeroplane at that weight.

If conditions are very smooth and you are very au fait with the aeroplane you may be able to nibble off a bit and fly the approach at 1.2 * Vstall.

Of course adjust for other factors as required in particular gusty conditions.

FD

Say again s l o w l y
30th Oct 2004, 15:17
I wouldn't ever recommend raising flap at that stage, all sorts of odd things may happen, what would you do if you then got assymetric flap for example?

Use the correct techniques, try out some shortfield landings on a longer runway until you get a feel for the machine, before trying short strips. The 172 is an incredibly docile machine, it just needs a bit of practise like any other.

Try doing some upper airwork at speeds just above the stall, this helps build up "feel", something I think that is more important than numbers sometimes.

FD's suggestion is a good one.

RUDAS
30th Oct 2004, 15:18
thanks a lot for the input...much appreciated:ok:

Shaggy Sheep Driver
30th Oct 2004, 15:57
Agree with SAS and FD - sounds like you're too fast down the approach; that's the only reason it'll float when it should land - but at least it sounds like you're flaring it properly, not driving it on nose-low as so many 172 drivers do - until one day the noseleg says 'stuff this for a lark' and breaks off.

The 172 is a lovely machine to land if flown at the right speed, those super Fowler flaps fully extended, to a correctly fully flared nose-high touchdown making full use of that sensitive elevator. Don't mess with the flaps - leave them down as Mr Cessna intended, and the aeroplane will be a pussycat to land.


As an aside, last Saturday morning two of us about to start our Concorde guide duties at Manchester were chatting when we noticed a Virgin 747-400 approaching 24R. It touched down fully-held-off, well nose high, with it being difficult to note the exact point at which the wheels took the weight - the gear just slowly contracted as more weight came off the wings and onto the wheels. The pilot kept the nose right up high, almost to the point of stopping on the runway, before it was gently lowered to the ground and the aeroplane taxyed off at the next taxyway. Beutifully done - we had both stopped chatting to watch, and it was a pleasure to witness someone really on top of their game like that.

SSD

Gertrude the Wombat
30th Oct 2004, 16:20
Do few stalls like that. Easier said than done :) - I've just got back from my SEP rating re-validation flight in a new 172 and in several configurations it really wasn't easy to persuade it to stall at all without doing quite ludicrous things to it.

I practiced short field landings in one of these recently and found that 60 over the fence worked, anything higher and it floated forever.

Whipping Boy's SATCO
30th Oct 2004, 16:28
Our 172 SP does fine with full flap and 61kts IAS.

Say again s l o w l y
30th Oct 2004, 16:43
One point, I wouldn't ever describe any Cessna (apart from the citation) as having a 'clean' airframe, marginally less draggy perhaps!

Final 3 Greens
30th Oct 2004, 17:33
RUDAS

IMHO, the 172 is a very underrated flying machine, it has a very effective wing that generates loads of lift and must be flown at the right speed "over the numbers."

I wouldn't b*gger about with the flaps if I were you, but I might consider ASI position error.

What speed does the book say you should approach at? If you are flaring enthusiastically, could your ASI be under reading? Are you flyig solo or one up?

Sounds to me as if a few circuits with an instructor could be helpful, really get to grips with the beast.

Although most of my hours have been on PA28, I have about 30 on 172s, from the F model to the P (not the R though) and that lovely wing keeps producing lift down to about 30kts :D

Flyin'Dutch'
31st Oct 2004, 05:36
Although most of my hours have been on PA28, I have about 30 on 172s, from the F model to the P (not the R though) and that lovely wing keeps producing lift down to about 30kts

A stalled wing produces no lift. That happens to the 172 at speeds well above 30KTS.

FD

Final 3 Greens
31st Oct 2004, 07:29
FD

I missed out the word "some" before lift, my typo and if we are being careful with words, the whole wing does not stall at once, it stalls progressively due to the washout built into the aerofoil profile, with the resulting pitch down being somewhat above 30 knots ;)

Halfbaked_Boy
31st Oct 2004, 09:52
Yup, if you check out a Cl/AoA curve you'll see a wing does produce lift below the stalling AoA :p

(although try not to keep that in mind when you're gliding down the runway at 55 knots considering raising flap :cool: )

Cheers,

Jack.

fu 24 950
31st Oct 2004, 12:52
the last time i was on this forum was about the flap raising issue, you will not "slam dunk " onto the ground if you are only 3 feet up wend you retrack flap. Short landing .. Two most important thing's; speed and most important is ROD, You can have the best speed control in the world, but if it is to flat you will float. You have to be :Behind the drag curve and need power to control the rate of descent, control speed also by power and that thing at the very back of the aircraft, drive it all the way to the ground and at the last moment round out , add a small amount of power to arrest the ROD and stop. Taxi alllllllll the way to the end of the strip

shortstripper
31st Oct 2004, 18:50
Spot on FU!

SS

IRRenewal
31st Oct 2004, 20:56
Halfbaked_boy wrote

Yup, if you check out a Cl/AoA curve you'll see a wing does produce lift below the stalling AoA Let's be glad it does. Aviation wouldn't exist otherwise. It even produces lift above the stalling AoA.

Regards

Gerard

1McLay
1st Nov 2004, 01:28
retracting flap on landing can be quite helpful...During the initial stages of the touchdown, retracting flap will provide you with a little sink to help shed off that float and most importantly once on the ground puts more of the weight on the main wheels sooner giving you much better breaking performance. This far outweighs any drag they may be providing during the landing roll.

alphaalpha
1st Nov 2004, 10:11
Rudas:

I have a Reims Rocket, but previously have frequently flown other 172s, particularly the P model.

Other people have made the point about speed control on final approach. 60kt is right for a normal short field landing, perhaps a couple of kt slower if at light weight.

However, what about power? Some instuctors teach the advantages of leaving on a 'trickle of power,' particularly when flying four up. This does tend to produce smoother landings, but will cause a lot of float. If you're looking for short landings, make sure the throttle is closed as you flare.

AA

Say again s l o w l y
1st Nov 2004, 10:28
You shouldn't ever have to resort to raising flap to reduce float. This is an artificial reduction in lift, rather than just flying the a/c correctly.

Why shouldn't we play with flap in the flare?
1) Assymetric flap retraction.
2) Pitching movement caused by movement of the centre of pressure.
3) Time. How long does flap retraction normally take?
4) If you are floating, you normally have too much speed, so if you retract drag flap, you will slow down less quickly. On Cessnas, the 40 flap setting is not there to primarily increase lift, but to increase drag. So why would you get rid of it?

Fly the machine correctly and you won't have to resort to daft things like retracting flap in the flare.

fu 24 950
1st Nov 2004, 10:42
I am a believer in raising flap if the need arises, BUT as SAS has just posted, it should not be needed.Speed and trottle control all the way down, flare to arrest the ROD, close the trottle and touch all as one movement.

Final 3 Greens
1st Nov 2004, 10:57
SaS

I agree entirely with your view.

Unfortunately, as a matter of fact, the 172R has only flaps 30 as land flap, since the 40 degree setting was deleted on the P or N model (can't remember which.) It's a shame, as that last 10 degress gave some very useful drag.

Still, it shouldn't need test pilot tricks to land ;)

Dumping lift, once all three wheels are down, is another matter. I believe (from memory) that the POH for one series of the Cherokee 6 mentioned this in the short field landing context - but you need to have a manual flap lever and it's a technique that would make me nervous in a retract, where there's too much risk of pulling the wrong knob! And you have to do it by feel, since looking in at this stage is pretty risky.

Say again s l o w l y
1st Nov 2004, 11:00
Ah yes! I can't really understand why they got rid of the 40 setting, as you say a very useful thing, especially on shortfields or when you've bu**ered up an approach.

david viewing
1st Nov 2004, 11:14
I can't really understand why they got rid of the 40 setting

The dear old 150 I trained on couldn't climb with flaps 40 and I believe go-around accidents were behind the change. Maybe someone has chapter and verse.

Say again s l o w l y
1st Nov 2004, 11:33
But the Go around drill is always to increase power, carb heat cold and reduce flap in stages to 15. If people are trained correctly, then this should never be a problem, but then again maybe cessna are scared of law suits. How sad.:(

tunalic2
1st Nov 2004, 11:45
Well considering Cessna stopped producing aircraft for 10 years for that very reason I think they probably are!

I like the 40 degree option too
it is after all only an option
T2

bcfc
1st Nov 2004, 12:12
A chap I knew had to force land a 172 solo and used 40 degree flap. Unfortunately, he skidded through a gap in some trees in a hedge and both wings broke and folded back.

With the flaps in their barn door configuration, they had sliced through the back windows and god only know what the outcome would have been if there were pax in the back.

Whipping Boy's SATCO
1st Nov 2004, 13:30
.......... and that is of course why one should always do a flapless forced landing. :ugh: :ugh: :ugh:

Final 3 Greens
1st Nov 2004, 13:37
Good way of stopping quick, though :}

coopervane
2nd Nov 2004, 00:22
I once inadvertently selected flap up from flap 30 on a go around!

Any flap change on the 172 means a load of pushing forward on the control column but this flap change leaves u pushing like Arny and gluing your eyes to the ASI hoping the speed will will increase quickly!

Short field landings in the beast are as previously said, all about speed and nailing the attitude during the approach. Don't flare too soon and chop the power when u think you are over the hedge.
The rest is down to how your cards are dealt on the day!

Coop & Bear

catswhisker
2nd Nov 2004, 10:42
Actually David V, the wee 150 could climb with full flap. In my very, very early days, I flew all the way to Downwind on a go-round with Flap 40. (One of those extended newbie brain-farts) The climb was slow, but not non-existent. That said, it felt very odd. And yes, I do know it's not the best way to carry on.

But aren't they forgiving little machines??

fu 24 950
2nd Nov 2004, 11:43
Coopervave, 'chop the power when u think you are over the hedge' sorry not quite right. The flare, the throttle closed and the touch down is all one action, If you are closing the throttle 10 feet up you still have no control on the touch down spot, and for strip flying this is not good. You must be able to hit the spot every time in a full stall , No yes \no \maybe

slim_slag
2nd Nov 2004, 13:09
fu 24 950,

what do you say to those who chop power downwind abeam the numbers?

Final 3 Greens
2nd Nov 2004, 16:10
Slim

"Autorotate" - see FU24s profile for explanation - explains a bit about the underpinning theory too ;)

BTW, FU24 is a Fletcher Ag aeroplane, bit of a short strip animal.

rodneyblois
2nd Nov 2004, 18:53
One not often discovered reason for abandonning 40deg flap settings...
On early model 40 flap versions..try a very low speed approach with full flap. say at about 45kts ias. if you are too high on approach and apply full slide-slip (max rudder) the diverted turbulent airflow from the 40 deg flap over the tailplane will cause an instant and complete tail-plane stall with sudden violent nose down pitching moment.
very alarming and clearly fatal at less than 50ft agl.:{

ontrackfor
3rd Nov 2004, 08:15
Nice point rodneyblois , i hadn't considered that.

I was told the reason flaps 40 was elimated from the 172R was that some pilots were having difficulty holding forward-pressure at max power in a go-around.

From the 172R POH: Stalling speed.

Vs-clean: 44KIAS. 1.3Vs = 57KIAS

Vs-full flap: 33KIAS. 1.3Vs = 43KIAS

fu 24 950
3rd Nov 2004, 09:28
Slim, (a) put the power back on and (b) if it has number's it is a airport, not a strip. Also can we get away from saying "chop power", it sound's rough, where as "closing the throttle " is a better term to use .

Brooklands
3rd Nov 2004, 12:33
Point of information.

The last mark of 172 to be have the 40 flap setting was the 172M. Subsequent marks only have 30 degrees. The later models also have the "lever-in-a-slot" rather than the switch and gauge for lowering the flaps.

(at least this is true of the M, N, P, R and S models of 172 that I've flown)

However the 182 still retains the 40 degrees setting.

Brooklands

FullyFlapped
3rd Nov 2004, 14:25
Brooklands,

At the risk of being pedantic ....

The last mark of 172 to be have the 40 flap setting was the 172M. Subsequent marks only have 30 degrees
Not so, my friend : the N also has 40 degrees available, and they work very well, too !

FF :ok:

slim_slag
3rd Nov 2004, 17:02
fu 24 950

Obviously you understood enough to answer the question.....

Cannot say I agree with you, but that's one of the highwing/lowwing debates. So nice to land a plane on the exact spot you chose when flying downwind, with no power from abeam the numbers. And if you are trying to get onto a real short strip with lots of high trees at the end there's nothing better than slipping it in (power off).

Ag pilots know nothing of this of course, they think you need oxygen above 50ft AGL :)

Final 3 Greens
3rd Nov 2004, 19:36
try a very low speed approach with full flap. say at about 45kts ias. if you are too high on approach and apply full slide-slip (max rudder)
an instant and complete tail-plane stall with sudden violent nose down pitching moment.

This is a design feature, to save the undertakers (morticians) a job in burying people trying to win a Darwin award and remove their genes fromm the pool , for the greater good of humanity.

1McLay
3rd Nov 2004, 19:53
SAS

I dont blame you, but you obviously haven't done too much short strip bush work have you? Don't knock it until you've tried it.

Think about it too instead of firing all guns at once.

Asymetric flap is pretty uncommon, not that it would pose as much of a problem as during a go around.
The pitching moment is almost unnoticable bacuase you are on the ground before it has time to show, but it would help actually, you are raising the nose further, further increasing AOA and drag.

Remeber when you first learnt to fly that, the aircraft will stall at a higher speed with flaps up, this serves to reason that if you want to stop the thing from flying and not come off the ground again (due to wind gusts, bumps in the strip) than getting rid of the flap is going to have that wing stalled sooner rather than later. Again I stress that because of the reduced lift, there is more weight on the mains giving you better breaking.

Just so you are aware, I'm getting rid of the flap just prior to the wheels touching the ground. I only do this when I need to (short bush strips, heavy loads).

Remember you can get float when you dont want it from gusts of wind too, not just because your speed is too high.

Where I work, your attitude would kill people. I suggest if your are competent enough with your 172 than you try a few experiements with retracting the flap after and just before landing and see what happens.

BTW for short field technique, I use 60kts and 55 short final (in certain consditions).


1M

Brooklands
4th Nov 2004, 12:28
the N also has 40 degrees available, and they work very well, too !

Oh dear - I must try and learn to stop answering from memory - it obviously isn't what it used to be (to be fair its at least a year since I flew an 172N).

I've had a look in my check lists, for the short field speeds and found the following (with the caveat that for maximum performance you should refer to the POH for the specific aircraft)

172 models L, M, N, and P
Short field approach, full flap 61KIAS
Normal approach, 20 flap 55 - 65 KIAS*

172 Model R
Short field approach, full flap (30) 62KIAS
Normal approach, full flap 60 - 70 KIAS

172 Model S
Short field approach, full flap (30) 61KIAS
Normal approach, full flap 60 - 70 KIAS

*No, I don't have an explanation as to why the speed range for a normal approach is below the short field approach speed.

Brooklands

Halfbaked_Boy
4th Nov 2004, 15:06
IRRenewal,

Let's be glad it does. Aviation wouldn't exist otherwise. It even produces lift above the stalling AoA.

Oops! Got words mixed up there, I meant to say ABOVE :p

Cheers,

Jack.

jonathang
6th Nov 2004, 01:07
Brooklands: *No, I don't have an explanation as to why the speed range for a normal approach is below the short field approach speed.

I also wondered about when I recently set foot in a 172.

All other GA aircraft I have flown during a short field approach use speeds lower than the Normal Powered Approach speeds.

The short field approach in the 172 feels remarkably like a NPA without the unusually higher nose attitude, high power to arrest rate of decent and lack of flare.

I figured the speed was high to cover accidents caused by screwed up short field landings. Since the Cessna's book landing distances are very short even without the short field technique.

In the S model with a Vs0 = 40Kias. 61 kts is close to a 50% margin. I would assume you could increase the landing performance even at MTOW by reducing the speed below this and still maintain a safe margin above the stall.

However would not be too keen to meddle with speeds decided at certification.

Any ideas?

Say again s l o w l y
9th Nov 2004, 00:47
Hi 1M,
Nope, my experience in 172's is limited to grass strips in the U.K. as an instructor, rather than as a bush pilot. Very different disciplines!

I can see where you are coming from, but I would definately kick a student up the a**e if they tried lifting flaps with me, rather than getting the speeds right.

If someone is just having difficulty with getting the a/c where they want it in a 'normal' environment, such as a 500m strip here in the U.K, then they need to practise the basics rather than trying out wierd and wonderful techniques, that may have their place in your world, but not for a low hour PPL.

In this situation dumping flap wouldn't help the fundamental problem of too much speed.
I'm very careful of what I suggest to inexperienced people sometimes, since their exuberence can sometimes overcome their (current) skill level. As they get more experienced, then different techniques may become more appropriate, but nothing can ever compare with getting the fundamental skills down pat.

The world of professional flying is very different from what we are describing here. To be honest there are procedures I use in my day job that would lead me to have a fit if I saw a student using something similar.

I'm just wondering, when dropping into a short, dusty, hot and high field whilst fully loaded up, do bush pilots do the calcs before hand? Doing that sort of flying leaves bu**er all space for mistakes or problems, not a situation I want any of my students to find themselves in (or myself for that matter!). A pro bush pilot may take all this in their stride, but should a 100Hr PPL, who maybe flys a couple of hours a month, even contemplate this sort of thing? Horses for courses and all that....

If you have to dump flap to get in somewhere, then IMHO you shouldn't be there in the first place! I assure you that having that attitude will keep you alive alot longer than any "tricks of the trade."

I will try raising the flap after landing, but I bet that it makes stuff all difference in this environment, whilst increasing the workload. Gusts are all part of the game and the speed should relevant to that. 50% of the gust speed added to the Vat.

The whole relationship between lift and drag, weight and braking efficiency is very complex, I don't see that the difference in braking efficiency is relevant, how many people use even 70% of the braking capability? Unless you are right on the edge of locking up, then the improvement is unimportant.

Your experience tells you one thing about this, mine another, I suppose its all about how you look at it.

1McLay
9th Nov 2004, 06:05
Hi SAS

Thanks for your reply. I totally agree with you sir about being careful of what you are teaching your students. It's something I wouldn't be teaching my PPL students either.

Operationally however it is not something we have to be doing to get into the strip however it makes life much easier. This of course as you rightly said is the difference between your and my environment.

But picture a bush strip thats around 3500 ft asl, that is by no means flat, a lot of undualations, has water pooled on it when it rains and any wind can be unpredictable and gusty on a good day. The strip length maybe a little under 500m, not straight and about 10m wide surouned by mountains thousands feet higher. This is a good bush strip. Ideally you want to get on the ground where you have planned (for example just on the other side of a water puddle).

So you put the plane where you want it but are immediatly sent skyward as you ride up a small undualation at 50 odd knots, so again you're airborne with little rudder control, the crosswind now takes you off the side of the narrow runway and into rough tussock and rocks, the thing is sinking again and a go-round is inevitable, so here you are low, slow and weighted, the last thing you want is sink, but hey just to keep you working you get sink, now you are below the strip and down in a river, strugling your guts out to get Vy. This has actually happened to me in a matter of seconds, however I was a passenger and i tell you now, it wazs pretty scary stuff. Shouln't be there, you got that right!

But alas it happend, and you learn from it.

Retracting that flap is gonna keep that thing on the ground, it will ride over the undulations and wont come unstuck and I needn't inslut your intelligence but when the wheels are not on the ground you haven't any breaking performance at all.

Remember generally the TAS is going to be higher than the IAS at altitude too.

if you mean weight and balance than yes, because these are CTO's. A lot of it however comes down to proficiency on A/C and in these environments. Knowing your aircraft and what it can do are very important as with any operation. This type of flying can be very rewarding in its own unique ways.

Kind regards

1M