The International Cessna 170 Association

Just curious to see what kind of TAS folks are getting from their aircraft. I have a -used- but not abused ragwing and I usually get 105-110 mph TAS. I know the manuals are always optimisic and my airplane has had some use so I don't really expect to get what the book says I should. Wondering if there is any difference between the ragwings and other models also.

My '53 170B has a McCauley EM 7655 (cruise) prop and it runs about 103-105 kts at 2450 RPM. But at that power setting with that prop it's probably more like a 70-75% power setting. My fuel flows run about 8 gph. The same settings with a standard 7653 prop would likely be about 65% and would run about 7.5 gph with TAS around 95 kts.

gahorn wrote:My '53 170B has a McCauley EM 7655 (cruise) prop and it runs about 103-105 kts at 2450 RPM. But at that power setting with that prop it's probably more like a 70-75% power setting. My fuel flows run about 8 gph. The same settings with a standard 7653 prop would likely be about 65% and would run about 7.5 gph with TAS around 95 kts.

(This is a test of the quoted reply.)

Mine is a 7653 prop and I get about 100 kts at 2450 and burn 7.5 gph.

Dale

Hi Jack;
I have a 53B model with a DM 7651 McCauley prop. I usually plan for 100kts. I usually have to run a little harder when I run with other 170s(usually close to 2550-2600rpms); but as Dale M & Glen Dee can attest to, I ran more economically on most of our Alaskan trip, than either of them(averaging 7.3-7.4gph). I lean aggressively both on the ground and in the air. I have 2 Dm 7651 props and am thinking of trading or selling one for a MDM 7653 or MDM 7655; or maybe even repitching one to a 53. My strip is 1500 feet long; so the 51" pitch is nice on those hot summer days with a load.
Jay

My '54B has a DM7652 prop. TAS @2450 RPM & 6000' usually works out to about 115 MPH. I can't attest to the accuracy of the indicated airspeed used to calculate this TAS.

N1981C is a relatively standard 1954 Cessna 170B with the standard C-145-2 engine, 7653 prop, 1200 SMOH, original wheel pants. I have the Horizon Instruments electronic tach so I am sure my rpm readings are accurate. I regularly fly by manifold pressure using 23.5 inches at low altitudes which gives 2400--2500 rpm. At 7500-8500 I get 21.5 inches and 2660 rpm and that is where I prefer to cruise. Indicated is 124 mph and true is 135-138 mph on 8.3-8.5 gph. I got the same speeds on 8.0 gph before installing the one piece venturi in the carb.

At the recent Sun-n-Fun I ran in the Sun 60 timed race and was the only four seat plane in the field with less than 150 hp. My speed was 128 mph mostly due to being new to racing. I flew by the first turn by about a mile looking for a white SUV marking the turn point. The vehicle I saw ahead turned out to be a highway survey crew. I had taped up the top and bottom of the struts and many gaps including the right door and baggage door neither of which fit well. During the race the rpm was at or above redline, indicated airspeed was about 155 mph but that may be reflective of my static system and the fact that I had taped the cabin vent openings closed. I have never seen more than 145 at full throttle before. There was considerable wind and GPS speeds varied from 128 to about 165 mph on the three legs. It was a learning experience and gives me a baseline to check out certain mods I hope will help the old bird go faster. HOW ABOUT SOME MORE 170's NEXT YEAR? IF THERE ARE THREE PLANES OF A TYPE WE ALL GET PRIZES.[/b]

I usually get 100 knots (on the GPS in dead calm) at 2350-2400 rpms using 8.3-8.5 gph of autofuel. I running an 0-300A with standard 76/53 prop. I guess that's about average for most of us. It will go a bit faster at 2450 but pushes up the gals > 9. It goes really fast downhill though!

Ernie in Va Beach

I usually see between 112-115 mph at around 2450,depending on temperature,humidity and what color shirt I'm wearing. I used to average around 7.5 gph or a little higher--since my engine overhaul,it seems to be burning an average of 8 gph or maybe even a little more. Somebody else mentioned that their fuel burn went up when they switched to a 1-piece venturi,maybe that's what made my burn go up.Been wondering about it but never considered that the new (exchanged,overhauled) carb had the 1-piece.

1478D has the C145 and DM7653 prop. In a steep spiraling dive the airspeed is a consistent 160 MPH. Atposheric conditions were cloudy and cold. Fuel flow was unknown.

Before I repitched my prop (it was a 48 ), I would average about 95 kts and 6.3 GPH. Recently repitched the prop to a 53 and I think I'm getting a little over 100 kts and 7.5-8 GPH. Obviously, I am able to get more power before becoming RPM limited.

I have a 1948 with Razorback fabric, so it's a little heavier than the norm, but I'd say that's about right. 100 MPH, at about 2200 RPM (I have a cruise prop). Sometimes it drops to 90 and sometimes it bounces up higher. I just set it around 2200-2300 and enjoy the ride.