Flap Setting for Landing

[pall]

One flight instructor of repute (wise grey head) told me it is preferable to land with full flap if possible as this is the recommended practice in the POA.

I often choose to land the C172N with 30º instead of 40º flap. Later models are produced without 40º flap.

What do ppruners recommend?

[bfisk]

I have personally never flown a 172 with 40 deg flap - only thing I know is they are supposedly poor climbers on a g/a with 40 flap...

In general more flaps will allow you to land at a slower speed, giving less ground roll, less brake wear. On rough/soft surfaces the low speed gives you less chance of nosing over, etc.

The cons I can think about are
1) Reduced airspeeed -> reduced airspeed over control surfaces -> less control autority. Might be something to consider in a nasty crosswind.
2) The flaps themselves will also act like sails in a crosswind condition.
3) For practice, landing at different flap settings is good.

[rmcdonal]

Rmcdonal shudders at his last memory of landing with 40Flap in a 172. Twas a sunny (hot) day, with a moderate load on board (Chockers), landing at a strip with a bit of character (Dirt road that bent a bit in the middle). Short final had us in a bit of light chop (hit a wily wily) and the CP (Happened to be in RHS doing check flt) called go-around. We made it (change undies), but since that day I have never used 40flap ever again.

It is actually harder to land with 40 then 30 anyway. But hey that’s just me.

[Lefthanded_Rock_Thrower]

Fly it as per the FM, if you do not and have an accident, the insurance company will not pay up due to "in-proper operation of Aircraft".

[TLAW]

I believe the POH says "40 degrees or as required," which gives you a bit of leeway. As you said, later models reduced the full flap setting from 40 degrees to 30 degrees, make of that what you will.

The view is a bit sporty with full flap, lots of muscle power required to round out and best not to chop the throttle too early. Pulls up quick, though. Not sure if full flap is 'required' if you've got plenty of runway. But wise grey heads are grey for a reason, I reckon.

[Escape_Slide]

I have to agree with Lefthanded_Rock_Thrower on this point.

1. Operate the aircraft in accordance with the aircraft flight manual. Under regulation 138 of CAR 1988 the pilot is required to comply with the information and instructions in the aircraft flight manual.

2. If you believe there is a better way to operate the aircraft, discuss with the owner/lessor of the aircraft.

3. The owner/lessor of the aircraft should contact the manufacturer to ascertain if this is an approved operation and this information should be sent from the manufacturer to the legal/lessor owner of the aircraft.

4. The owner/lessor should then apply to CASA to have the procedure approved and this may require demonstration flights to be conducted. This results in an approved supplement being issued to the aircraft flight manual. This is then the responsibility of the registration holder to maintain.

5. Pilots who have not flown the aircraft in this configuration and want to fly it, must then be briefed on, trained in and be able to demonstrate competence in the operation of the aircraft in this configuration.
:cool:

[Richo]

Hi all

Firstly, there is an approved mod for 40 deg flap Cessna's which limits the flap selector to 30 deg and changes 1 (only) page in the AFM or POH. This is very common in Aus reg 40 flap Cessnas. This mod is not mandatory and there are still a few of the old beasts getting around out there. They are very popular with farmers etc due to the reduced rwy (paddock) lengths required.

Secondy, while I whole heartedly agree that LHR and others post about following the AFM, I must point out that the AFM/POH for these aircraft does allow the use of flap settings other than 40 deg and provides an ADVICE (admitedly no charts) for the adjustemets to the landing/takeoff distance. One, and the most common area to find such information is in the crosswind landing advice (both normal and expanded procedures) to limit the flap used.

So Pall to answer your question,
Your wise OLD grey instructor is correct, fly the aircraft to achive the performance the manafacturer designed, tested and certificated the aircraft for. But always KNOW your aircraft, read the AFM/POH, know what the manafacturer has made allowances for and what ADVICE or INFORMATION is provided.

So can you use 30 deg flap in the old N model, yes you can the POH does allow for it. Can you do it and achive the performance as shown in the P charts, No. (unless you have the modified aircraft and charts).

PS He may be old and grey, but he is not a guru unless his licence number starts with a 0 (zero).

richo

[Andy_RR]

If you have to fly the POH every time, how do you ever get a chance to practice a flapless landing? Or is that considered an emergency procedure only to be flown pax-less?

A

[Ralph the Bong]

The general philosophy is to use as high a flap setting as posible. Such a practice gives the best landing field performance and the slower touchdown speed is kinder to the brakes and tyres. There are variations to this, as with anything related to aviation.

A reduced flap setting may be required under the following situations:
1) High airfeild elevation- The climb wt. or approach wt. limit may require a lesser flap setting

2) Engine out operation-see above.

3) Wind conditions- A gusty wind may require approach at a higher speed for better aileron control. There are 2 ways to do this : either fly the approach a bit faster (using an approved speed additive schedule) or use a reduced flap setting that gives a higher Vapp.

4) Windshear- It amases me how few people can configure an aircraft to cope with windshear. Long ago, I did some auditing of feeder carriers (2 crew turbo prop ) for my employer. I was gobsmacked that professional (so they claimed) pilots would engage in the following practices in windshear conditions:

i) Use high flap settings so as to make a particular taxi way.
ii) Using an aiming point that was around the 150m marker, or shorter.
iii) Turning off the ILS as they dipped below G/S on ILS RWYs (so as to avoid GPWS warning of being low on slope).

Presumably these 'geniuses' are still plying their trade back in Oz. Perhaps even training other new hires and polluting the industry with their poor technique thus breeding another generation of people that cant really fly. Oh well, sad really.

[readbackcorrect]

Always found the 40 to be both a treat and novelty and would select 40 any day given the opportunity. Found the handling characteristics better and a nicer descent profile (steeper). Shame there arent more a/c like this, although G/A was a little more challenging but the particular a/c 172 i flew had 180 hp anyway

[Three Blader]

Having spent over 1000hrs in 172s operating off short and rough strips I use 40dg for a Calm-Modarate day and 20-30dg for X-wind and winds up to 30 knots on the nose

[turbolager]

why on earth would you want to lock out the selection of flap 40? I'd way rather fly the 172N than the gutless/lardy 30flap 172R models :}

[Cloud Cutter]

The reason is pitching moment on go-around. Too many yanks were killing themselves, and the brilliant American legal system practically forced Cessna to reduce full flap to 30 degrees on the R model and later. This is the same reason the STC for 180 HP C172s includes reduction to 30 degrees max flap.

[Centaurus]

Three Blader. You said:
Having spent over 1000hrs in 172s operating off short and rough strips I use 40dg for a Calm-Modarate day and 20-30dg for X-wind and winds up to 30 knots

30 knots crosswind? Doesn't the POH say at page 4-3 something about max demonstrated crosswind velocity for take off and landing in the C172N is 15 knots? It is called sticking your neck out if you deliberately exceed the limits. Something about duty of care, comes to mind.

[rmcdonal]

I think it means strong x-winds, and winds up to 30kts (not x-wind)

[Cloud Cutter]

And max demonstrated crosswind component is not a limit. You can quite safely, and legally exceed 15 knots crosswind in a 172. As far as I know, cessna do not publish a max crosswind limit.

[haughtney1]

Another 1000+ hr ex One seventy two driver here (been a while though) and all the 172's I flew were the 40 flap versions.

I cant say I ever used flap 30.....and yep landed with around 25kts cross in taumaranui one day, didnt seem to be a big deal..a bit gusty..a bit twitchy..stall warning going off now and then..but it can be done:ok:

Personally I think cessna handicapped the later models with only flap 30...regulated to cope with the ham phisted idiots who dont understand the aeroplane:hmm:

[Capt. On Heat]

The mod to limit 172's to flap 30 also upped the MCTOW by 100kg/lbs (too long ago to remember which sorry-thinking lbs though) from the flap 40 MCTOW.

[Cloud Cutter]

I think with 30 degrees and 180 HP the MCTOW went from 2300 lbs to 2550. For the 160 HP R+ models, it's 2450.

[flash123]

I always tought if its a solid x-wind or even gusty but not varying or backing use full flaps, if its varying use less flap (being you will actually get it on the ground, flap 40 and 15ts from the side coming onto the nose just makes you float down the runway all day unless you like wheel barowing..

[gassed budgie]

Normal landing approaches can be made with power-on or power-off, with any flap setting desired.

The above is straight out of the 172 POH (1978 172N). That's what Cessna recomends, but you'll generally find people sliding down final at 65 to 70kts with full flap. I tend to use 30 degrees of flap at 65kts, it just feels right (to me). I find with 40 degrees of flap it takes a fair bit of power to drag the poor ol' girl down final and when you get there it takes a bit more of a tug on the yoke to round out and hold off. For short fielders it's 55kts and full flaps for me, 60kts if it's a bit blustery.
It goes on to say.....


Steep slips should be avoided with flap settings greater than 20 degrees due to a slight tendency for the elevator to oscillate under certain combinations of airspeed, sideslip angle and centre of gravity loadings.


a bit further on........


If flap settings greater than 20 degrees are used in side slips with full rudder deflection, some elevator oscillation maybe felt at normal approach speeds. However, this does not affect the control of the airplane.


It doesn't say that slips with full flaps are prohibited, only that they should be avoided. And so they should if that's what the manufacturer recomends. It may be different in the later 172's built after 1996. The laywers wrote the POH's and they recomend you don't set foot in the aircraft as it may lead to serious injury or death! One more.......

The maximum allowable crosswind velocity is dependant upon pilot capability as well as aircraft limitations. With average pilot technique, direct crosswind landings of 15kts can be handled with safety.

Again it might be different in the later 172's (someone might be able to enlighten me on that) but there is no maximum crosswind or maximum demonstrated crosswind component quoted in the POH. From experience I can say that once you get to 23 to 24kts, that's it. No more rudder left to play with.
One other thing regards crosswind landings. It seems to me today that the newer generation of young pilots coming up through GA, seem not to be able to successfully negotiate their way through a crosswinder which is a real shame. The technique is simple and relatively easy to master with practice. It seems as though they were never shown in the first place.
And one other thing while I'm thinking of it. Flap travel was limited to 30 degrees on the 172P and later models because the gross weight was increased by 100lbs (and more in other applications). Under the certification criteria the aircraft must meet certain climb gradient parametrs with full flap. Hence the reduced setting at the higher gross weights.

[Cloud Cutter]

That IS the max demonstrated crosswind (15 Kts). There is no max crosswind.

[pakeha-boy]

mate...use flaps 40 for sure as other posts have reccommended........but on short runways.....practice dropping the flaps to 30 in the flare,..itll get you on the deck real quick and makes for a brilliant landing...(old bush trick)....reckon this wll get a raise out of a few boys:} ...PB

CC ....good point...all max crosswinds are 'Demonstrated"

[haughtney1]

PB....

What about just as you flare..ya dump the bloody lot:ok: (manual flap)

Works on a REALLY short strip:} (usually in a 180/185:ok: )

[pakeha-boy]

..great minds ...think alike.:ok: .....cheers mate

[pall]

Thanks to all posters. This has been a great discussion. I have learned heaps from it. You can't beat experience. This is pprune at its best.