40deg flaps

Peter Ha

Peter Ha

Pre-takeoff checklist
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Hey folks,
My plane has 40deg flaps.
What’s pro & cons of using that much flaps?
 
The pro is that you can fly slower without stalling. The con is that you are less able to withstand wind gusts.

The above is not necessarily true if 40 degrees of flaps are equipped on the wrong plane.
 
Pros: gives you options for adjusting you approach to landing.
Con: not really a con but your flare will have to be timed more accurately. Once you do flare your airspeed will bleed off much quicker
 
what is the maximum degree of flaps one can use slipping an Arrow?
 
RingLaserGyroSandwich said:
The pro is that you can fly slower without stalling. The con is that you are less able to withstand wind gusts.
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40 deg doesn't lower stall speed any more than 30, it just adds extra drag, which is good for landing.
 
Velocity173 said:
Don’t slip with 40 degree flaps. ;)
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I suspect the emoji there is supposed to clue the poor hapless poster into realizing the above is sarcasm. But in case he didn't catch it, THERE'S NO REASON NOT TO SLIP A 150 with full flaps.
There's darned little reason to even be concerned about it in certain 172 where some manuals advise against it.
 
flyingron said:
I suspect the emoji there is supposed to clue the poor hapless poster into realizing the above is sarcasm. But in case he didn't catch it, THERE'S NO REASON NOT TO SLIP A 150 with full flaps.
There's darned little reason to even be concerned about it in certain 172 where some manuals advise against it.
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Exactly! Do it all the time in mine.
 
Make sure to start to pull the flaps out as early as possible on a go around. The O-200 doesn't have a lot of oomph to drag the plane around with 40°of flaps. Especially on a warmer day.
 
Another con of 40deg flaps is related to go around. In the 182 at least in a go around its throttle full, carb heat off and immediately flaps 40 >> 20. Then as you build up speed and altitude do the standard 20 >> 10 and then 10 >> none.

Another is aborted soft field landing. The approach is with flaps 40 unless high crosswind. My first CFI burnt me on this one (simulated). Right as we touched down he shouted abort. So I gave it full power, carb heat off but forgot to initiate the flaps immediately from 40 >> 20. That actually isn't a very good scenario though because once you touch down on something really draggy like wet sod I'm pretty sure the flaps going 40 >> 20 might sink you in the mud before the extra power pulled you out. But it was a interesting combo which I am guessing he may have experienced.

Another place they are great is if the tower ask you for best forward speed for landing. With 40 flaps available you can really book (no flaps) right into short final and then kill off speed quickly via 10, 20, 40. Of course if this makes you uncomfortable you can use the magic word (unable) and go practice it more to be ready to accept it in the future.
 
The O-200-A is at best a 97 hp engine at 2750 rpm, and in a C-150 it won't generate enough rpm to give you anything close to that on takeoff, or on a rejected landing. A C-150 with the Sensenich 69CK at full throttle has a static rpm between 2470 rpm and 2320 rpm. The McCauley 1A100/MCM has a static rpm between 2475 rpm and 2375 rpm. The McCauley 1A101/DCM 21 is the only climb prop option for a C-150 but the static rpm is still between 2600 rpm and 2500 rpm.

Cessna limited the flaps on the C-152 to 30 degrees maximum, rather than 40 degrees maximum on the C-150. That's largely because on a hot day at anywhere near the 1600 lb gross weight, if a pilot got a Cessna 150 back on the power curve (around 50-52 mph and below the 58 mph approach to landing speed with flaps) with 40 degrees of flaps, he'd be in a descent even at full power. The only way to gain airspeed in that situation is to either retract the flaps to around 20 degrees, or lower the nose to reduce the angle of attack. Either way it means trading altitude for airspeed, so if the pilot delays too long, there is no arresting the descent.

40 degrees of flap rather than 30 degrees on a C-150 has very little effect on minimum stall speed (48 mph versus 48.5 mph), but it does significantly increase drag. That said, if you need more drag, you are better served by a slip, as you can quickly add, and just as quickly remove drag with a slip, and you can add and subtract drag proportionate to your needs. The lack of a 40 degree maximum flap setting on the C-152 is not something many people miss.

If a possible rejected landing is anything other than a remote possibility, 20 degrees of flap makes far more sense in a C-150 or C-152. The stall speed is still only 49 mph, and a C-150 will still climb (poorly) at 1600 pounds with full power on a hot day.
 
Larry Vrooman said:
The lack of a 40 degree maximum flap setting on the C-152 is not something many people miss.
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I beg to differ; I learned to fly in 150s just as the 152 came out. The lack of that last 10° of flaps upset a lot of people, it was just another useful tool pilots had, and then didn't have any more.

We always almost used full flaps for landing. In the event of a go around we were taught to retract the flaps in increments, slowly, and give the plane time to accelerate.

'Course that was a long time ago, and I've never owned a plane with flaps at all. But all of my planes have had adequate rudder so I never missed 'em.
 
Love the 40 degrees in my '57 172 gives you more options. Admittedly most of the flap over 20 degrees is just drag but you can come down like an elevator. With the johnson bar flaps getting them out quick if you need to is not a problem.
 
I love them for getting into short strips with obstacles. It is an elevator ride down.

If you leave them down on a go around it will go bad quick
 
You can make the first turn off if landing with 40 degrees of flaps. In a stiff headwind you can almost do a vertical landing.
 
Grum.Man said:
False! Stall speed is noticeably slower with 40 degrees.
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Nope, lift does not increase from 30 to 40 deg. Max lift actually occurs right around where your ailerons are set for max deflection which may even be a little less than 30. Everything else is drag not lift.
 
I didn’t realize 40 degrees was typically for drag only and not also slower speed into the flare. I only ever flew a landing with 40 degrees of flaps once haha.
 
What could go wrong with 40 deg of flaps? Another inattentive pilot taking the active. A cow walking across the RW. A wind shift. What ever.
It will seem like an eternity to retract electric flaps from 40 to zero in a pinch. Hydraulics like on an old Mooney are a little faster coming up. Manual flaps are the best. They come up like a switch blade when needed.
The old BirdDog was delivered with manual flaps that came down 60 deg. The old guys from that era liked them a lot. Then they converted them to electric. Most guys then only used 30 or 40.
The old 150 had an AD (1970's) to change the flap switch. When you lowered flaps, and released the switch, it would snap back to the up position. Zero flaps would not be noticed if your eyeballs were on the RW.
Check the POH. Not much difference between 40 and 30 deg. However, the FAA defines a "normal" landing as one with full flaps.
 
Flaps are fun! More flaps, more fun.

Had a sailplane with 90deg flaps and the ailerons moved with the flaps. Great fun there for sure!


Sent from my iPad using Tapatalk Pro
 
Pitch for 50(or whatever, been a while)and you can come down like a helicopter which is awesome. Not so great for going around but you won't really need to.
 
Could always do what was done in the B727

Throttle.jpg


A bolt was placed between the flaps 30 and 40 position to keep from selecting 40. Flaps 30 was the standard landing configuration.
 
Peter Ha said:
Hey folks,
My plane has 40deg flaps.
What’s pro & cons of using that much flaps?
Click to expand...

Pro: It adds a lot of drag, so you slow down quicker during flare. The deck angle during flare will also be lower, allowing you to see a bit more over the nose during flare.
Cons: You can kill yourself if you attempt a go-around with full flaps. Cross winds will require a more aggressive correction just prior to touchdown due to the slower speed.
 
I fly the 150s predecessor the cessna 140, its flaps have far less drag than a 150s, i do notice a lift difference, but very little slow ya down effect.. but my point is; we can leave em at 0 and still make a steep approach and land short, with the old slip, which is “tunable” as you go... In the 172 i like 20, i can always slip yet i can still climb if i need to: the best of both worlds, and thats how id fly a 150...
 
Everything about landing with 40* flaps is better EXCEPT a 150 doesn't have enough power to climb in a go around with full flaps. Balancing advantage and risk is up to the pilot.

40* flaps allow a lower AOA without gaining speed. Lots of drag allows a steeper final approach. Both are very good things.
 
The one thing I can say about the flap switch in a 150 (the one I had you held down to lower but it would allow you to lock it in the up position) is that if you take your finger off the switch abruptly the thing can spring through the off position and bounce into up-and-locked. It was very disconcerting to find that the flaps were retracting on short final.
 
Putting in 40 deg of flaps on our 182 give me that big iron feel. That extra drag gets noisy. Have to throttle up pretty good and it stops on a dime but you don’t really flare and “try to not land” like 20 deg flaps. Whole different feel.
 
As a student pilot many years ago, I almost killed myself on a touch and go with 40 degrees of flap. Got airborne but couldn't climb out of ground effect. Fortunately there weren't any obstacles off the end of the runway, or I wouldn't be here typing this today.
 
Doc Holliday said:
Could always do what was done in the B727

Throttle.jpg


A bolt was placed between the flaps 30 and 40 position to keep from selecting 40. Flaps 30 was the standard landing configuration.
Click to expand...

Was that all 727’s? Was doing that because of an accident?
 
Don't spin your 150 with full flaps. Got a story about that.
You can come in very steeply with the barn doors out, for sure.
Note that a 150/172 will be flying so slowly that you'll have little control authority. Got a 'decorative' propeller in my music room 'cuz of that.
 
Stewartb said:
Everything about landing with 40* flaps is better EXCEPT a 150 doesn't have enough power to climb in a go around with full flaps. Balancing advantage and risk is up to the pilot.

40* flaps allow a lower AOA without gaining speed. Lots of drag allows a steeper final approach. Both are very good things.
Click to expand...

If what I’m reading above is true, that there is almost no difference in stall speeds between 30 and 40, then it’s not a lower AOA. You get a lower ‘deck angle’ and steeper angle of descent, but not AOA.
 
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