The International Cessna^® 170 Association

A climb prop is always going to climb proportionately better than a cruise prop. A cruise prop is always going to cruise proportionately faster than a climb prop.
Under normal conditions, I'm never going to fly 115 mph with the 8043 and you're never going to climb 1000 fpm with the 7653. The takeoff performance chart in our manual projects about a 75% longer takeoff than actual and I havn't looked at them since realizing they do not apply to a modified plane. The opposite holds true with the cruise charts, however the Sea Plane Cruise Chart does track pretty close to my actual.

I have been to Leadville in my rag wing with two people and 25 gallon of fuel. was not a problem. I went early in the morning. If you can get out of ground effect you will make it out as its like taking off an aircraft carrier. If you can fly at 12000ft on the way in and you are early in the day with light winda aloft it shouldn't be a problem. They train in 150 hp 172s but they say they never fill the tanks. The day I was there a fellow with a straight tail 150 came in and left no problem. When I fly in the CO Rockies I try to find a place to get rid of my baggage so I can keep the plane light as possible. Flying my 170 into Leadville was one of the high points of my flying career. (no pun intended) Bill K

Agreed Bill. Flying into Leadville for the first time is definitely a rush. Here's a shot the buddy who flew in with me took of me and my Tcraft at Leadville.

AW SHUKS GAY HORN ISNOT THU CHIKORIE INNA MY COFFEE! ISA JUICE MASHED OUT O CANE, SOURED AN REFINED BY MASSICOYT DOWN THAR IN OLE BREAUX BRIDGE.

You are correct about the A/S vs G/S. But it still stands to reason that if you need 100 mph indicated just to get flying, a climb prop lacks the "high end" to CONTINUE to do the job "properly".

The first "mountain flying" trip we took in our '52 was to Durango, CO in 1973. It had the original 76x53 prop in place. On our way out west we stopped at Gallup, NM for fuel. Of course, being a mountain flying newbie, I filled the tanks to the top. Went into FSS and got a WX update that showed severe clear and no surface wind. Didn't ask about DA! As we started our takeoff roll I noticed some reluctance on 93D's part to accelerate to flying speed. I really got the heebie jeebies when I looked out the side window and saw them 8:00x6s spinnin like I was goin about a 120mph and the airspeed indicating only 80 and it wasn't flying anything but the tail. Fact is when I gently pulled back on the stick the tailwheel went right back to the runway surface with a thump. My actions should have been to abort but with 10000' of runway I let her fly off. Lift was barely enough to clear the fence on the airport boundary and it took lots of shallow turns to clear the small hills westward of the airport. That my friends was my first encounter with high density altitude. Lesson learned, lighter is better, cooler is better and enough wind on the nose is essential!

Later flights in and out of high altitude environments were with the 76x55 Cal Twist prop mounted in place of the 76x53. I bought it from an aircraft supply place in Torrence, CA. Fank Snarey was working there at the time and he had lots of praise for this prop. I carted it home to Kansas City as "carry-on" luggage! (God bless old TWA! ) After I bollted it on I noticed good takeoff performance and markedly better cruise numbers.

Knowing a little more about "mountain flying numbers" I have flown many hours in the mountains and have no complaints in the 170's ability to fly out of high altitude airports. Know the D/A, load lightly and know your limitations as well as that of your 170.

Under normal conditions, Plane X climbs at 1000 fpm and Plane Y climbs at 500 fpm.
When DA increases so that Plane X can only climb at 500 fpm, what is Plane Y climbing at?

All though it took longer than usual and he only climbed out at 500 fpm, Plane X went home and made faces on the 170 forum , while Plane Y was still galloping down the 10000’ ft runway, trying to reach 100 IA, so that he could get back to his cane juice.

Just returned from my trip out West; Knoxville, TN to Page, AZ. The old 170 does pretty well as long as you pay attention and always stay conservative. We flew into Las Vegas, NM on the second day. The field sits at 6900' and has 8200' of pavement. Tougher getting in with the remnants of the hurricane making strong crosswinds. Topped off in the morning and just below gross I can clear a 50' obstacle and that is about it until I can get some speed and suck up the flaps. I can manage about 300' a minute while circling over the field before heading out. Went to Double Eagle next after crossing the ridgeline at 65kts. Next was Farmington, NM which is lower at 5500' but by then it was 2pm and hotttt! Got six gallons in my light wing and headed to Page. This time I followed the riverbed off the plateau from the airport while my airspeed and climb increased. I also have the 7653 prop which as an intermediate prop does alright. I have found that being at gross makes a huge difference from being 100lbs. under gross in all aspects of performance. I have used the gps to average out my speed and it always works out to 105kts. Good luck with Leadville!

philnino wrote:...The field sits at 6900' and has 8200' of pavement. Tougher getting in with the remnants of the hurricane making strong crosswinds. Topped off in the morning and just below gross I can clear a 50' obstacle and that is about it until I can get some speed and suck up the flaps...

Phil,

At first I thought you might have done better by leaving the flaps retracted for takeoff at that altitude, but then I remembered that you have an A-model. Checking the performance charts, I was surprised to find that under most conditions the takeoff with the second notch of flaps is much shorter than with no flaps. Your take off run still seems quite long anyway. The book says an A-model can clear a 50-foot obstacle in just over 4000 feet at a 7000-foot elevation at 100 degrees F.

Miles

Miles,
I got off the ground just fine in about 3200' but I remained about 50' off the deck till I was at the end of the runway. I used the second notch but she does not like to accelerate with that much or climb that well so I build a little steam and drop to the first notch. I was climbing initially at about 65-70 indicated until I get rid of everything and can accelerate to 75-80. What kind of performance are you getting and is there a better technique? Thanks,
Phillip

Notice that only the B-model airplane actually publishes Flaps extended takeoff performance charts. (In other words, take off with flaps deployed is not a documented procedure except in the B-model airplane.)
Although a sentence or two in the ragwing and A-model infer that takeoff distances will be shortened by use of flaps....there is actually no documentation to support that inference.
This is important to the operator for a couple of reasons. Above a certain density altitude the use of flaps will lengthen takeoff distance. This is because as density altitude increases the drag of the flaps is greater than any lift produced by them. This is especially true of the ragwing and A-model due the nature of their plain flaps.
This is also documented with the B-model because the B-model actually has documented flaps-extended takeoffs. Above approx. 6,000' Density Altitude, the use of flaps will penalize the B-model takeoff distance. (It is likely a slightly lower altitude which will penalize the earlier airplanes.)
So if your density altitude approaches 6,000', ...it is better operationally to take off with zero flaps. (Further, the loss of performance during flap retraction in such takeoffs is penalizing. In other words, a loss of alittude, airspeed, or both will occur as flaps are retracted in such conditions.)
See the performance charts in the Owner's Manuals/AFMs.

George,

My bad! I misread the chart on p. 11 of the A-model owners manual linked on the Memebers Only page. The "Flaps Down" portion of the performance chart applies only to landings, and I didn't catch that on the first look. Confusion also comes from the lines on page 9 and 13 that states that the shortest takeoffs are with 2 notches of flaps. Too bad they didn't do the testing; it probably would have save a few pilot seats over the years.

Phil,

One reason I like the manual flaps on our airplanes is that we can control the RATE of extension and retraction. When I do use flaps for take off, I retract them SLOWLY, and give the airplane a chance to accelerate.

Miles

Yeah, this matter is a common consideration with a lot of airplanes, not just 170's. Most transport multi-engine aircraft, especially jets have well-documented performance charts which can more easily illustrate situations where they have to reduce their flap settings for takeoff in high density altitude conditions just in order to project that they can continue to meet climb requirements after takeoff. It's possible in some such conditions to take off and lose an engine and find that climb or level flight cannot be maintained, neither can the aircraft accelerate to a speed which will allow the flaps to be retracted. Catch 22.
The solution is found in charts that use lesser flap or zero-flap settings and longer runways (because the lesser flap selection will extend takeoff rolls) in order to have reduced drag and be able to climb after takeoff. Although we're not dealing with the multiengine loss-of-an-engine thing, the same situation applies to our little 170's as regards the ability to climb after takeoff. In theory at least, in extreme cases, it might be possible to take off into ground effect with flaps in the takeoff position....but be unable to accelerate either out of ground effect due to the drag of the flaps.... OR accelerate to a speed which would allow the flaps to be retracted and not settle back to the ground.
Watch those density altitudes and compare matters with your aircraft's performance charts.

On this subject (as an illustration of this very sermon I ignored one day), Jamie and I took off from Winslow, AZ http://www.airnav.com/airport/KINW (elev: 4941) on rwy 29 (7100' long)
on the way to the Las Vegas convention. We were travelling as a flight of two, in company with Cleo and Louise Bickford and we'd stopped here for lunch and fuel. We were full. Rwy 29's threshhold was closer to the gas pumps at which we'd just finished refueling. No reason to spend any more time in this blistering heat taxing over to the other runway. (Didn't bother to note that it was 7500' long. Rwy 29 looked much longer than anything a 170 would need.)

N146YS has a McCauley 7655 cruise prop. It's not exactly a climb performer even on a standard day. It was in the afternoon and it was hot. Real hot. Cleo and Louise Bickford were waiting to take off behind us in Wendell and Shiela Wyborny's B-model with a standard prop.
Rwy 29 slopes upward from 4870' elev at the approach end, to 4899' elev at the departure end. (Yet another interesting factoid ignored by the idiot flying my airplane.) The cacti and scrub continue this gentle upward slope for quite a ways. A small wooden shed sits on the westward horizon.
Runway looked real long. At the beginning. About half-way down this thing I finally saw about 60 mph indicated and with the tail in the air I rotated a bit and the airplane kinda went into a "dance" with it's wheels each taking turns doing a tap dance on the asphalt like it was so hot it hurt the plane's bare feet. About another eternity it finally came up into ground effect. And stayed there. It quickly ate up sufficient runway as to make an abort look impossible. The end of the runway slid under the nose and here came the cacti and scrub. I had to side-step slightly to avoid a 10-foot tall scrub oak. About a mile later we flew by the single-story whitewashed shed. We almost had 80 indicated and not a lot otherwise was happening. It simply wouldn't climb. Any attempt to increase pitch only resulted in a loss of speed. I was mentally beating myself up pretty good about now, mentioning things to myself about stupidity and ....well....I was saying some things that Jamie had never heard me say before as the rising terrain was staying just about where it had been for the last mile or so. We were stuck in ground effect and couldn't get out of it until I finally nursed the thing very gingerly to about 90 mph indicated, at which time it finally picked up about a 200 fpm climb.
I don't remember exactly what his words were, but Cleo broadcast some remarkably succinct comment about that time that it'd be OK for me to go ahead and climb out now, because he was taking the runway!
About the only thing I could have done to worsen the situation would have been to attempt that takeoff with flaps. The airplane might have come up into ground effect a bit earlier....but there'd be no way to have ever gotten it to accelerate out of it, and with the gently rising terrain I'm pretty sure it would have turned even uglier than it was.
I simply wasn't thinking about the things I should have been thinking about before beginning that takeoff. I was on vacation and so was my brain and any professionalism I might ever have possessed.

PS-Jamie had energetically helped load the plane back at home. When I unloaded at Las Vegas, I came to realize I was somewhat "off" on what our load was as well. Some of those bags were filled with stuff a lot heavier than they looked. Now I always load everything personally on such trips. (And Jamie and I've both learned we don't need nearly the things we thought we'd need at our first convention.)

George, I believe the A model flaps are more closely compared to plain flaps than split flaps. They do provide a modicum of lift, just nothing like the fowler flaps, but the drag is much higher. In my experimentation, I can get off the runway quicker by deployment of flaps, I just can't accelerate very quickly. In the case of high DAs it would probably be pretty tricky trying to milk flaps and reach best climb.
The method of popping 20 degrees of flaps on the roll like the manual mentions works pretty well at elevatoring you up to 50 feet or so, but the trade off is you are generally much slower, that might not be so good in a high DA/gross condition.
David

I agree with performance changing in regards to the setting of the flap position on the takeoff roll at high density altitude. The manual states that the shortest roll will be with flaps in the second notch. My experience this past trip was that I could get airborne at gross 6900' elevation at 65 degrees in about 3200' but I could not accelerate or climb much out of ground effect. I realize this does not seem to make sense as one would have expected the climb to continue with the aid of the flaps. I found that by slowly easing out the flaps I could accelerate and therefore climb. I really was circling the prairie avoiding obstacles making this work. I did not think to try and takeoff with flaps 0 and compare as I was comfortable with what was working. I later used one notch but did not see any appreciable ground roll change. I know that high and hot in jets definately changes the numbers and flap settings but without the charts and only your (Miles') response a few months ago on performance for the 170 above 7000' I did what I thought would work. Maybe next year I will try and write down some numbers.... It would be nice to know as she does like to hobby horse with the higher ground speed and the rudder is very slow to correct. Could be technique!!?!

Ooos, David! You're correct! I did not realize I'd writen "split" and should have written "plain". (I frequently make that mental-picture error due to my penchant for thinking of twin-Cessna's I've flown that usually have split flaps.) I'll edit that msg to correct the error so as to not cause confusion over the matter.. Thanks for pointing out my error.

Yes, philnino, that's what I was referring to. A zero flap takeoff would likely result in better performance in climb, at the expense of takeoff roll.

If I could just get my hands on some first, second, and third segment charts maybe I could land the old girl on top of Everest and takeoff......I guess I will have to recertify above 15500' first! Maybe I will need that dual TSIO-360 field approval after all....

Seriously, I would like to hear about others experiences with this matter of flap, no flap takeoffs above 7000' DA.
Phillip