Hi all,

I just recently joined this site and have really enjoyed the posts that I have read thus far. I have a 1969 172K and fly out of KBJC near Denver. I'm not sure if this has been asked yet, but I would like to improve the short field performance and at the same time add some safety factor to what's generally considered an under-performing airplane at higher DA's. I've read that the Sportsmans STOL kit is a great addition to this plane, as is the Powerflow exhaust. My question is for you folks that have done these STC's, which mod would I benefit most from? I'm from Idaho and enjoy going up there often, and would like to eventually work up to some of the awesome backcountry strips of my home state. I also just removed the flap gap seals from the wings, and really noticed an improvement in flap effiency. Looking forward to hearing about everyone's experience.

Welcome.

Re-pitch prop to climb specifications.

Thank you Mr. Maule,

Yes, I have considered that, but I have also read that some folks report a significant increase in RPM's with the powerflow. I currently have a cruise prop on her, and if I change the exhaust I'd like to see where the RPM's max out at with the mod. If I can stay within the redline with a flatter pitch after the exhaust mod, I'd totally do that. How was you climb rate improved with the re-pitch?

In a tired C-170 I put an 80/43 McCauley on the front & took the 76/53 off. I gained 300 FPM climb but lost approximately 12 knots. Best money I ever spent for performance.

byeBill

IMHO:

Immediately remove the rear seat, and enjoy an immediate 35 lb. gain in useful load, improved climb rate, significant reduction in risk, and improve overall safety at ZERO cost. By doing so, you have now made an under-powered airplane into a reasonably-powered airplane. Make sure to compute a new weight and balance sheet for this config. in case of ramp check. Put the rear seat in a permenently sealed glass case in the back of your hangar, and install a sign on the glass case saying "In case of 180HP engine upgrade, break glass."

Next, remove all obsolete or non-functioning instruments, heavy carpeting, etc. that does not serve a good useful function for YOUR mission and YOUR density altitude. If you are not that concerned about speed, removing wheel pants will save one or two gallons of gas in weight.

Next, inspect your exhaust system using a probe camera up the wazoo. Make sure your mufflers are not damaged or falling apart, creating restrictions in your exhaust flow (power loss and safety issue).

Have your ignition harnesses and spark plugs tested PROPERLY, to see if you're getting all the oomph out of your mags at that altitude. Make sure your timing is set at the most advanced setting within the allowable range, or as far forward as your high-altitude-knowledgeable IA mechanic will allow. (see cooling system comment below)

I believe there is an approved K&N air filter element, which will give you slightly higher manifold pressure (less delta-P across the filter element) than other filters. Manifold Pressure is like football and adult films... it's a game of inches.

Make sure that your air box flapper valve is sealed well, and you have no leaks or lossess in the intake system.

Put in the effort to make sure your engine cooling system is functioning well, with no leaks or gaps in the baffling, and make sure it cools well. On a warm summer day, when everything is against you, the last thing you want is to have to fly the airplane faster than optimum climb angle, in order to keep your engine cool.

Flap gap seals may not help climb but aileron gap seals will slightly. There is no "slot" effect or benefit from the aileron gap, only lost lift and drag.

BCP member 182STOL Driver is a certified Cessna rigging technician. Proper rigging makes any airplane fly better any time, but at high density altitudes you will further benefit slightly by having your airplane rigged with the flaps and ailerons flying at the lowest possible end of the legal/acceptable range. You are essentially "drooping" the trailing edge in the same direction as high-dollar STOL modifications, but in a fixed position instead of retractable. This is in effect creating more camber in the wing, making more lift, which in your situation you need more than minimum drag. Again, there is a legal rigging range which you should not exceed. But this measurement should be taken in "flight" conditions which means air forces lifting upwards on flaps and ailerons, not simply "at rest" on the ground. You want the flaps and ailerons "drooped" to the maximum allowable amount in flight with air pushing up on them. Regardless of who rigs your airplane or where in the acceptable range you are rigged, the flaps MUST be at or slightly below the same height as the ailerons both inflight AND on the ground, the flap trailing edges must NEVER be above the ailerons. Never.

As for add-on purchased items, the VG kit is by all reports the best bang for the buck at least on an electric flap Cessna.

Not my words - but some things I've been told by guys with several thousand hours flying back country strips in 172s:

Even with the 210hp engine, they are still not going to compete with other aircraft in their power class for STO performance, but they are up with the best of them on L if you've got the skills. This is in regards to planes with CS props (read good TO pitch but Heavy with a capital H).

So based on that, I think if it were me I'd focus on improving takeoff rather than doing short landing mods. Spending a little on hp and more on weight reduction, as it seems hp isn't the whole story here. Like EZ says there are some quick wins with weight & VGs. See the bigrenna 185 thread - do you need all that insulation?

But maybe with a bigger tire up front to get the AoA steeper during the TO roll....? Or with flaps which don't take 10 seconds to extend so they can actually be used to help get airborne? Dunno if those STCs exist - never flown either of those in a 172, but those are the things I'd be looking at. You could always pump up the front oleo, seems an easy win?? You see plenty of 172 sitting low in the nose.

My rear seat was exactly 30 lbs. I had my mechanic make up two W&B forms, one with the seat, one without, so I can put it back in if I want to haul someone in the back seat.

My 172 has flap gap seals. The previous owner told me that they helped the climb rate a little, but didn't let it descend as fast with full flaps. I've never flown it with them off, so I don't know the nature of any differences or if his piloting technique might have influenced his perceptions. It seems to me that the flap gap seal would keep the high pressure air under the wing for a little more lift, and at high altitude the mighty O-300 won't let it achieve the high angles of attack that could benefit from the "slot effect"

Once you get some good instruction in the airplane, from a crusty, nasty, irritable old instructor who has gray hair, and once you have ABSOLUTELY impressed that instructor with your stall, spin, incipient, accelerated, and all other low speed/stall related maneuvers... and ONLY after you have done all that....

You will see a very noticeable improvement in aircraft performance in virtually all flight phases when you are flying at 80-90% rearward CG. With your rear set removed (and keeping focused on lightening your load) this becomes more of a challenge, but you may find that you may have room for a tool kit in the "very rearmost" corner of the baggage compartment, which can remain there as long as your rear seat is locked in the aforementioned glass case. I have also noticed more than one Cessna aircraft that has had the rear tiedown ring/tailskid ground down over the years, and which could therefore use a little reinforcement in that area. I have also noticed that some of the wiring running to the rear of the aircraft (tail nav light etc.) can be in need of some electrical repair. Many old-school electricians favor lead solder in these areas.

Remember I said 90% of the CG range. Little or no benefit past that, and it becomes risk/illegal/stupid very quickly after that. Don't ask how I know.

Buy a Mooney!
errr...okay Idk!

After those, spend money on avgas and practice, practice, practice. We have a 172 with 180, powerflow vg's flap and aileron gap seals, on pavement 450 ft t/o and landing. takes practice though

I have a 63 P172D, 180hp Lycoming, CS prop. I had flap gap seals installed, mostly because I expected them to help cruise speed, and they do, by about 5-6 knots. If the seals hurt full flap performance, I can't tell it, and I have maybe 1500 hours or more in 172s. Do they help on take-off? I can't say that they do that, either. Their sole benefit appears to be to improve cruise speeds.

When I bought my airplane, it already had Madras droopy wingtips. They help with low speed control--and of course, they look cool!

I already have a very efficient exhaust--whoever cobbled it up when the engine STC was made did a great job, and my IA, who has installed several Powerflows, says that the only performance "benefit" I would get with a Powerflow would be a lighter wallet. Make sure your current exhaust system is unimpaired. My IA advises that most of his customers who have had him install a Powerflow notice a slight increase in performance, not nearly what Powerflow claims, but noticeable.

KN has a less restrictive air filter, and there are others as well, which also help a little. Make sure yours is clean.

There's no need to raise the nose with a fancy fork or by over-inflating the strut--if you do a soft field type of take off even on a hard surface and just raise the nose enough to get the tire off the surface, you've accomplished more than by installing an expensive after market fork.

Mine has manual flaps, but the electric flaps work fine, too--but at high density altitudes, you won't want to use any flaps for take off except for soft fields, anyway, until you swap the engine for a 180hp one.

I fly out of the Fort Collins and Greeley areas now, but for several years I instructed in 172s out of Laramie, 7277' MSL, often with DAs over 10,000'. You'd be surprised how well a stock 172 will perform, with proper technique.

Best bang for the buck? Practice, practice, practice, with the airplane loaded as you intend to fly it. Any 172 can get into a strip that it can't get back out of, so practice take-offs as much as landings. If you can't get down and stopped in 600' without excessive braking at Denver's altitude, you aren't trying. But getting back off regularly in less than 1000' will take practice--but it's doable if you keep it light, don't raise the nose too high, and leave the ground in ground effect. Stay in ground effect until you get the speed up--it's easiest if you start with nose down trim. Raise the nose too high, and you'll just mush. Do it right, and you'll do fine.

Cary

I have stock1963 145 hp 172 which I have flown and instructed in over 2400 hours, based at 3900ft 1400 ft runway. EZ said it all tune it up, keep it light, fly in the back country in the morning. I and the wife used it in the Idaho back country camping at many of the strips, Smiley Creek, Sulfer Creek, Johnson Creek, Indian Creek and others with no problem, probably the shortest would be Mexican Mountain Utah at 1300 feet. Buy a second prop with take off pitch, use the 70% rule, know when to use short field and soft field take offs, soft field at Johnson Creek when grass needs mowing and after being irrigated. Met a guy at Johnson Creek with a 150 Tri Pacer, when he came up from southern California he put on the takeoff prop, lowered cruise speed but he could take off and climb through the slot just like his buddies with the 180s.

Monte

best value by far is the sportsman STOL
0-360 and the mt prop made more difference but cost waaaaay more money.

EZFlap wrote:.........As for add-on purchased items, the VG kit is by all reports the best bang for the buck at least on an electric flap Cessna.

I disagree. the lure of a lower price than a stol cuff led me to install a set of micro VG's on my C150/150TD. After having spent the mney, I won't say that there was zero improvement.... but the mprovement was very subtle. I would not put VG's on a stock cessna wing again.

[quote="Battson"] Not my words - but ..........Even with the 210hp engine, they are still not going to compete with other aircraft in their power class for STO performance....[quote]

I disagree. I don't have any time flying them, but I know two different guys who own Cessna T41B's (military 172 trainer with an IO-360 Cont engine & c/s prop, about like a light Hawk XP) and I've seen them take off and climb out as good as or better than the average 180/182. Probably not at gross weight, and probably not as much payload as a 180/182, but great performers-- at least at sea level.

Here is My two cents, all have good advice, as for a Sportsman STOL kit I installed one on my 67H 172, My impression is, it took 10 to 15 MPH off landing and stall speeds and made the aircraft much safer below 60 mph without effecting cruse speed. Huge difference on takeoff speed and handling, will fly below 40 mph indicated AS, and feels solid @ 45 mph, the numbers used to be 55 and 60 mph. With the yoke all the way back it will not stall, only mush, aileron seals are part of the kit and they make a big difference too. Money well spent.

hotrod150 wrote:

Battson wrote: Not my words - but ..........Even with the 210hp engine, they are still not going to compete with other aircraft in their power class for STO performance....

I disagree. I don't have any time flying them, but I know two different guys who own Cessna T41B's (military 172 trainer with an IO-360 Cont engine & c/s prop, about like a light Hawk XP) and I've seen them take off and climb out as good as or better than the average 180/182. Probably not at gross weight, and probably not as much payload as a 180/182, but great performers-- at least at sea level.

I do fly around in this one on occasion (like this weekend), but I use the words of it's 4,000hr owner over my own. It's better than your average trainer for sure, a big step up. Takeoff is always harder to judge from inside, but climb performance is easy to compare, and compared to a 180 both loaded up...? No contest!

Hey all,

Thanks for the great responses and advice. I think I've come to the right place to learn more and chat about my favorite mode of transportation. Cary, that is interesting what your IA said about the Powerflow exhaust. I've read a lot of PIREPS that make it sound like a great mod to the O-320. Perhaps the reports I've read were somewhat influenced by folks that just had their pockets lightened by $4K. I might've said similar things in that case. I am however really liking everything I've read about the Sportsman's kit. Just seems like you get a better margin of safety. I don't want to spend the money on an O-360 conversion, since my engine only has 460 hours on it. Instead I'm more interested in improving both my ability and the plane's ability to safely fly at slower speeds. For those of you with the Sportsman's kit, was there a big learning curve with the new flight characteristics?

Bob

ID172inCO wrote:.... I've read a lot of PIREPS that make it sound like a great mod to the O-320. Perhaps the reports I've read were somewhat influenced by folks that just had their pockets lightened by $4K....

Very few people will want to admit that the latest hotdog mod they just spent $4K (or whatever) on didn't do shit. That makes it pretty hard to make an intelligent decision about doing that mod yourself. Since I only have $700 in my VG's, I can go as far as to admit that the improvement is "very subtle". (as in, don't blink or you'll miss it)

Perhaps the reports I've read were somewhat influenced by folks that just had their pockets lightened by $4K. I might've said similar things in that case.

Probably true. Just like noisy glasspacks on our cars when we were kids gave them "lots more power", right? My most recent example, tho' pretty cheap, was I created a muffler for the water heater exhaust vent for our home, then convinced myself that my efforts had definitely quieted that obnoxious rushing noise--but then "she who must be obeyed" said, "it sounds the same to me." Oh well!

Cary