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#88185 - 08/07/12 05:48 PM 172N with 180HP conversion = FUN
Awkward Bird Offline
Gold Pilot

Registered: 11/20/11
Posts: 1021
Loc: Boulder Creek, CA
Our club has a new plane that I got to fly yesterday evening. Its an 1978 172N with a 180HP engine in it. That plane can REALLY climb and cruise! especially compared with the other 172s I fly at the club. It even out climbed the SP I'm used to flying. It was very nose heavy during landing compared to what I am used to, but it was a blast to fly.

A little side question. I noticed this 172N has 30 degrees of flaps. I'm used to 40 degrees of flaps on 172Ns. Are there different flap options for different model years of 172Ns? Just curious.
_________________________
"I fly because I wouldn't want to do anything else." ~ A. Cluff
Musing and misadventures - http://imanawkwardbird.blogspot.com/

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#88188 - 08/07/12 06:07 PM Re: 172N with 180HP conversion = FUN [Re: Awkward Bird]
Pilawt Online   content
Club Sponsor
Gold Pilot

Registered: 02/13/10
Posts: 1448
Loc: Vancouver, WA
All 172Ns came from the factory with 40 degrees of flap.

If the 180 hp conversion on the one you flew was done with the Air Plains STC, there are actually two different STCs for the 172N.

The first is the conversion to the 180-hp O-360 engine. That STC alone makes no changes to the airframe aft of the firewall, and does not change the gross weight from the original 2300 pounds. Thus the useful load is reduced by the added weight of the engine.

A second STC provides for installation of a physical limitation in the flap mechanism (photo below) to prevent extension greater than thirty degrees. When that is done, gross weight of the 180 hp 172N is increased by 250 lb, to 2550 lb. Reason being, the airplane would not be able to meet FAA climb guidelines for balked landing with full 40 degrees of flap at the heavier weight.

My '78 172N happens to be one of the very few with the 180 hp engine and 40 degrees of flap. It was my dad's airplane before he passed away, and when he did the 180 hp conversion in 1997 he bought both of the STCs but never had the flap limit installed. So it still has the 2300 lb gross weight. That doesn't bother me much, because I like flying into short fields, and I have no friends. grin

I have the parts for the flap limit, and can have it done any time. But for now I like it the way it is.



The 1981-86 Model 172P, the 172Q, 172RG, and all "restart-era" 172s are limited to 30 degrees of flap from the factory, as well. The flap limit in the 172P allowed the gross weight to be increased to 2400 lb without an increase in power.
_________________________
Jeff Jacobs
C-172N-180
KVUO / Vancouver, WA


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#88189 - 08/07/12 06:14 PM Re: 172N with 180HP conversion = FUN [Re: Pilawt]
Awkward Bird Offline
Gold Pilot

Registered: 11/20/11
Posts: 1021
Loc: Boulder Creek, CA
Thanks for the quick info Pilawt! I had a feeling someone here would know smile
_________________________
"I fly because I wouldn't want to do anything else." ~ A. Cluff
Musing and misadventures - http://imanawkwardbird.blogspot.com/

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#88190 - 08/07/12 06:37 PM Re: 172N with 180HP conversion = FUN [Re: Awkward Bird]
Rusty Rudder Online   content
Diamond Pilot

Registered: 02/26/10
Posts: 5184
Loc: NorthEast
Very interesting, I would have rather had the 40 degrees than the paper that says 2550 on it... (I've got the 172 w/180 Penn Yann)

Good accurate info pw, thanx!
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#88196 - 08/07/12 07:30 PM Re: 172N with 180HP conversion = FUN [Re: Rusty Rudder]
Nintendo Pilot Online   happy
Gold Pilot

Registered: 05/22/11
Posts: 1688
Loc: Utah
That 180 HP engine is nice isn't it AB?
_________________________
1979 Cessna 172N (N9478E) w/180 hp conversion by Air Plains
Alan C.
PP-ASEL

Blog http://ontarget-spionen.blogspot.com/
Youtube Channel http://www.youtube.com/user/spionen007?feature=mhee

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#88255 - 08/08/12 01:55 AM Re: 172N with 180HP conversion = FUN [Re: Nintendo Pilot]
Nightowl Offline
Club Sponsor/Speed Demon
Gold Pilot

Registered: 02/14/10
Posts: 1826
Loc: Northwest lower Michigan
Our 172N has the 180 hp AirPlains conversion with the STC to increase max gross weight to 2550 lbs (restricting max flap extension to 30 degrees and beefing up tires to six-ply). It really does climb like a homesick angel, and we have flown often with four adults on board, so am very happy with the gross weight increase. I usually land with 20 degrees of flap or less and rarely use 30, so 40 would be overkill for our usual needs (our three previous Cessnas all had the 40 degree flaps, so definitely have used them in the past).

Another advantage is that our STC includes a change to the flap extension speed, allowing 10 degrees of flap at 110 kts, with any further flap deployment kept to 85 kts or less (just as the 172Q POH specifies). Dropping 10 degrees at 110 kts gets us down to 85 kts quite nicely, so this has proven to be very beneficial, especially on instrument approaches.

And yes, I've flown the 172P, R, and SP, and our airplane, being lighter, does outclimb them all. And it also can carry more passenger payload than our CAP 182T when fueled for a similar mission.

The 180 hp engine is what should have been in the 172 all along.

John
_________________________
CP-ASEL-IA
'77 C172N, AirPlains 180 hp conversion

Our sigmap has been flown entirely using aircraft with capabilities at or below those of the C-172.


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#88303 - 08/08/12 01:25 PM Re: 172N with 180HP conversion = FUN [Re: Nightowl]
Pilawt Online   content
Club Sponsor
Gold Pilot

Registered: 02/13/10
Posts: 1448
Loc: Vancouver, WA
One important benefit to the more powerful engine is that it allows one to maintain a higher airspeed while climbing, helping the engine to stay cool during a long climb on a hot day.
_________________________
Jeff Jacobs
C-172N-180
KVUO / Vancouver, WA


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#206047 - 09/07/14 02:50 PM Re: 172N with 180HP conversion = FUN [Re: Awkward Bird]
Rjplourde Offline
New Member

Registered: 08/19/14
Posts: 2
Loc: Ct, USA
Could anyone tell me what's involved with removing the 40 degree flap extension stop and what's the legalities of doing so?

Thanks

-Bob-
_________________________
-bob-

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#206050 - 09/07/14 05:02 PM Re: 172N with 180HP conversion = FUN [Re: Rjplourde]
Joeman434 Online   content
Gold Pilot

Registered: 02/19/14
Posts: 1125
Loc: Ocala, Florida
Sometimes I fly in and out of a 1200 foot grass airstrip....and for those times I' like the 40 degree flaps.
_________________________
Do it right the first time...a baker gets to throw his mistakes in the garbage....we don't!!

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#206100 - 09/08/14 07:58 AM Re: 172N with 180HP conversion = FUN [Re: Joeman434]
BNB-SP Offline
Bronze Pilot

Registered: 09/23/12
Posts: 523
Loc: FL
You cowboys are nuts. 1200 foot strip? I get anxious just flying on my 3000 ft runway!
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2004 182T
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#206118 - 09/08/14 10:49 AM Re: 172N with 180HP conversion = FUN [Re: Rjplourde]
EdW Offline
Club Sponsor
Gold Pilot

Registered: 11/21/10
Posts: 1223
Loc: Just east of Graceland
Originally Posted By: Rjplourde
Could anyone tell me what's involved with removing the 40 degree flap extension stop and what's the legalities of doing so?

Thanks

-Bob-


It's illegal, immoral and fattening, so we can't tell you how to do it.

Seriously, it would be illegal for you to remove any stop installed due to an STC or other approved mod without a Field Approval from the FAA. You must maintain your aircraft to either Type Certificate standards, or a legally modified condition.


Edited by EdW (09/08/14 10:51 AM)

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#206120 - 09/08/14 10:55 AM Re: 172N with 180HP conversion = FUN [Re: EdW]
vettdvr Offline
Club Sponsor
Diamond Pilot

Registered: 06/24/10
Posts: 6023
Loc: Slidell La
Removal of the 40 flap restriction that was installed under and STC is not only illegal but could lead to failure of the wing due to the very high stress loading on the rear spar in the wing. Even with the smaller engines 40% flap can crack the spar if the plane exceeds the flap limits. This is why if you have the 180 you DO NOT want to remove the restrictor and go to 40 % flaps due to much greater probability of spar failure.
_________________________
Vettdvr

Single/Multi/instrument/type/commercial But then I am still learning.

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#206122 - 09/08/14 10:57 AM Re: 172N with 180HP conversion = FUN [Re: EdW]
Rjplourde Offline
New Member

Registered: 08/19/14
Posts: 2
Loc: Ct, USA
EdW,
Thanks for your reply.
_________________________
-bob-

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#206128 - 09/08/14 12:31 PM Re: 172N with 180HP conversion = FUN [Re: vettdvr]
Pilawt Online   content
Club Sponsor
Gold Pilot

Registered: 02/13/10
Posts: 1448
Loc: Vancouver, WA
Originally Posted By: vettdvr
This is why if you have the 180 you DO NOT want to remove the restrictor and go to 40 % flaps due to much greater probability of spar failure.

I have the 180 hp STC, and have purchased but never installed the separate gross weight increase/flap restriction STC (see my post above). I operate within the legal 2300 lb MGW and within published airspeed limits.

How am I at greater risk this way than I would be if the airplane were still in its original configuration?? Is there documentation of C-172 wing or spar failure due to use of 40 flap?
_________________________
Jeff Jacobs
C-172N-180
KVUO / Vancouver, WA


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#206133 - 09/08/14 01:59 PM Re: 172N with 180HP conversion = FUN [Re: BNB-SP]
Joeman434 Online   content
Gold Pilot

Registered: 02/19/14
Posts: 1125
Loc: Ocala, Florida
Originally Posted By: BNB-SP
You cowboys are nuts. 1200 foot strip? I get anxious just flying on my 3000 ft runway!


I wouldn't do it on a 90 degree day in Florida....but a few private airstrips only have 12-1500 feet.
_________________________
Do it right the first time...a baker gets to throw his mistakes in the garbage....we don't!!

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#206136 - 09/08/14 02:05 PM Re: 172N with 180HP conversion = FUN [Re: Joeman434]
Joeman434 Online   content
Gold Pilot

Registered: 02/19/14
Posts: 1125
Loc: Ocala, Florida
"How am I at greater risk this way than I would be if the airplane were still in its original configuration?? Is there documentation of C-172 wing or spar failure due to use of 40 flap?"

I have never heard of any failures of the wing or spar. I have heard and seen flap distortion when somebody with the older type switch just dumps all the flaps above the approved arc.
_________________________
Do it right the first time...a baker gets to throw his mistakes in the garbage....we don't!!

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#206144 - 09/08/14 02:46 PM Re: 172N with 180HP conversion = FUN [Re: Joeman434]
Dave W Offline
Second in Command

Registered: 03/23/14
Posts: 162
Loc: Northern Virginia
Originally Posted By: Joeman434
"How am I at greater risk this way than I would be if the airplane were still in its original configuration?? Is there documentation of C-172 wing or spar failure due to use of 40 flap?"

I have never heard of any failures of the wing or spar. I have heard and seen flap distortion when somebody with the older type switch just dumps all the flaps above the approved arc.


I don't buy it ether, but still better not to become a test pilot. As far as I know the XP had 190hp and the same 40 degrees of flaps. The 175 had had 175hp and the same 40 degrees.

Edit: Just did some Googling. There doesn't seem to be a consensus as to whether or not the 175 wing is identical (except fuel capacity) to the 172. The type certificate is different and shared by the XP. So, possibly the Flaps are beefed up on the 175 and XP. I don't know.


Dave


Edited by Dave W (09/08/14 02:59 PM)

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#206158 - 09/08/14 07:41 PM Re: 172N with 180HP conversion = FUN [Re: Dave W]
SkyhawkAV8tor Offline
Safety Pilot

Registered: 01/30/13
Posts: 61
Loc: PA, USA
The second owner of my third hand '79 172N had a 160HP Airplains upgrade installed (don't know why he didn't go to 180HP). Manual calls for 40 degree lockout, which is not installed. I like using 40 degrees as I can make my taxiway with just a little bit of headwind on final. So far no failures. But I am the only one flying the plane and I don't dump them until I'm on short final.

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#206180 - 09/08/14 08:28 PM Re: 172N with 180HP conversion = FUN [Re: SkyhawkAV8tor]
Underdog Offline
Safety Pilot

Registered: 10/27/12
Posts: 86
Loc: TX
I am having difficulty following this thread.

The OP wanted to know if he could remove the restriction to 30 deg flaps and get back the 40 deg flaps.

A couple of people answered correctly, but the topic is getting sort of off track.

The answer is certainly, and with no danger. But it will need to be done by a mechanic with the proper entry for removing the stc, AND you will have to go back to the original stock gross weight. There is no danger, no test pilot stuff, nothing. You will just have a 180 hp 172 with a stock gross weight. The stc for the gross weight increase that limits the flaps to 30 degrees is entirely seperate from the engine upgrade. You can do the engine upgrade without the gross weight increase upgrade, but not the other way around. At least not to 2550 lbs.

There is also a 100 lb increase for the stock 172 that also restricts the flaps to 30 degrees, but that is only a 2400 lb gross weight (at least on the N model), no engine upgrade required.

Is this what the discussions were about or did I completely misunderstand... apologies if I did.

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#206288 - 09/08/14 08:49 PM Re: 172N with 180HP conversion = FUN [Re: Underdog]
Pilot110 Offline
Silver Pilot

Registered: 03/15/11
Posts: 874
Loc: Florida,USA
Our T-41B has 210 hp 2500 lb GW and 40 degrees of flap. It has the same wing as standard C-172 with long range fuel.

The rear spars had six cracks in them when I bought the aircraft, the other T-41B I looked at also had cracks in the rear spar.

There is a reason for limiting the flaps with a HP increase. I believe the CAP T-41B aircraft that were converted to the 180 hp O-360 engines also have the flap restriction with the 2500 lb weight due to the use of the STC.


Edited by Pilot110 (09/08/14 09:15 PM)

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#206365 - 09/09/14 06:59 AM Re: 172N with 180HP conversion = FUN [Re: Joeman434]
Pilot110 Offline
Silver Pilot

Registered: 03/15/11
Posts: 874
Loc: Florida,USA
Originally Posted By: Joeman434
"How am I at greater risk this way than I would be if the airplane were still in its original configuration?? Is there documentation of C-172 wing or spar failure due to use of 40 flap?"

I have never heard of any failures of the wing or spar. I have heard and seen flap distortion when somebody with the older type switch just dumps all the flaps above the approved arc.


Rear C-172 spar, the horizontal bottom crack ran all the way across the bottom between the rivet holes, the vertical top crack ran all the way to the end of the top edge of the spar. You are looking at one section where the flap hinge attaches. Every hinge point was cracked. BTW, rear spar cracks are quite common in C-172 aircraft, Cessna ran out of the rear spar repair kits a few years ago. Those large barn doors create a lot of load on the lightly built rear spar and the stress is aggravated by increased HP and higher GW.







Edited by Pilot110 (09/09/14 07:12 AM)

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#206386 - 09/09/14 09:21 AM Re: 172N with 180HP conversion = FUN [Re: Pilot110]
Dave W Offline
Second in Command

Registered: 03/23/14
Posts: 162
Loc: Northern Virginia
thanks for the photos, can the cracks be seen from in front of the spar where flaps mount without removing the flaps?


Edited by Dave W (09/09/14 09:22 AM)

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#206395 - 09/09/14 12:29 PM Re: 172N with 180HP conversion = FUN [Re: Dave W]
Pilot110 Offline
Silver Pilot

Registered: 03/15/11
Posts: 874
Loc: Florida,USA
Originally Posted By: Dave W
thanks for the photos, can the cracks be seen from in front of the spar where flaps mount without removing the flaps?


Dave the cracks are behind the flap hangers and are not visible. The way they can be detected is loose or missing rivets and flexing in the attach points at the spar. You can grasp the trailing edge of the flap and gently move it up and down watching the hangers to detect any looseness and twisting in the spar.

Pilots are so use to the sloppy loose flaps on the C-172 that shake when you grasp them they often overlook the loose hangers.

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#206396 - 09/09/14 12:58 PM Re: 172N with 180HP conversion = FUN [Re: Pilot110]
Dave W Offline
Second in Command

Registered: 03/23/14
Posts: 162
Loc: Northern Virginia
Originally Posted By: Pilot110
Originally Posted By: Dave W
thanks for the photos, can the cracks be seen from in front of the spar where flaps mount without removing the flaps?


Dave the cracks are behind the flap hangers and are not visible. The way they can be detected is loose or missing rivets and flexing in the attach points at the spar. You can grasp the trailing edge of the flap and gently move it up and down watching the hangers to detect any looseness and twisting in the spar.

Pilots are so use to the sloppy loose flaps on the C-172 that shake when you grasp them they often overlook the loose hangers.





Thanks, I'll check it out.

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#206398 - 09/09/14 01:29 PM Re: 172N with 180HP conversion = FUN [Re: Pilot110]
vettdvr Offline
Club Sponsor
Diamond Pilot

Registered: 06/24/10
Posts: 6023
Loc: Slidell La
Originally Posted By: Pilot110
Originally Posted By: Joeman434
"How am I at greater risk this way than I would be if the airplane were still in its original configuration?? Is there documentation of C-172 wing or spar failure due to use of 40 flap?"

I have never heard of any failures of the wing or spar. I have heard and seen flap distortion when somebody with the older type switch just dumps all the flaps above the approved arc.


Rear C-172 spar, the horizontal bottom crack ran all the way across the bottom between the rivet holes, the vertical top crack ran all the way to the end of the top edge of the spar. You are looking at one section where the flap hinge attaches. Every hinge point was cracked. BTW, rear spar cracks are quite common in C-172 aircraft, Cessna ran out of the rear spar repair kits a few years ago. Those large barn doors create a lot of load on the lightly built rear spar and the stress is aggravated by increased HP and higher GW.







These are the cracks I was referencing. A weak spar 40 flaps, more power (180) an Max GW on a go around might set things in motion.
_________________________
Vettdvr

Single/Multi/instrument/type/commercial But then I am still learning.

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