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Old 30th Oct 2004, 13:11   #1 (permalink)
 
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C172 short field landings

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
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Old 30th Oct 2004, 13:39   #2 (permalink)
 
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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.
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Old 30th Oct 2004, 14:16   #3 (permalink)
 
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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????
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Old 30th Oct 2004, 14:40   #4 (permalink)
 
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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
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Old 30th Oct 2004, 15:17   #5 (permalink)
 
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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.
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Old 30th Oct 2004, 15:18   #6 (permalink)
 
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thanks a lot for the input...much appreciated
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Old 30th Oct 2004, 15:57   #7 (permalink)
 
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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
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Old 30th Oct 2004, 16:20   #8 (permalink)

I'd rather be floating

 
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Quote:
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.
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Old 30th Oct 2004, 16:28   #9 (permalink)
 
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Our 172 SP does fine with full flap and 61kts IAS.
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Old 30th Oct 2004, 16:43   #10 (permalink)
 
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One point, I wouldn't ever describe any Cessna (apart from the citation) as having a 'clean' airframe, marginally less draggy perhaps!
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Old 30th Oct 2004, 17:33   #11 (permalink)
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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
 
Old 31st Oct 2004, 05:36   #12 (permalink)
 
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Quote:
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
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Old 31st Oct 2004, 07:29   #13 (permalink)
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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

Last edited by Final 3 Greens; 31st Oct 2004 at 07:40.
 
Old 31st Oct 2004, 09:52   #14 (permalink)
 
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Yup, if you check out a Cl/AoA curve you'll see a wing does produce lift below the stalling AoA

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

Cheers,

Jack.
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Old 31st Oct 2004, 12:52   #15 (permalink)
 
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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
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Old 31st Oct 2004, 18:50   #16 (permalink)
 
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Spot on FU!

SS
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Old 31st Oct 2004, 20:56   #17 (permalink)

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Halfbaked_boy wrote

Quote:
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
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Old 1st Nov 2004, 01:28   #18 (permalink)
 
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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.
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Old 1st Nov 2004, 10:11   #19 (permalink)
 
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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
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Old 1st Nov 2004, 10:28   #20 (permalink)
 
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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.
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