Cruise prop T/0 vs climb prop ?

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pdb
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Cruise prop T/0 vs climb prop ?

Post by pdb »

Hi,

I will be departing from Alaska to the east coast by way of eastern Oregon in late June and am nearly certain that I will be replacing my 80 42 climb prop for my cruise prop, a Cal Twist (McCauley DES 1C172 MDM7655) for the trip.

I will have one pax and camping/survival gear and full fuel for most of the legs. I am concerned about what this prop will do to r/c, especially for some of the higher elevation airports (>4,000 asl) and the higher density altitudes we will see this summer.

Does anyone have experience with this prop or a similar cruise prop with respect to the change in r/c and service ceiling that I may experience in these conditions? I will be confined to long paved strips so I can except long takeoff rolls but
I will have to clear some high terrain.

Thanks,

Pete
Pete Brown
Anchorage, Alaska
N4563C 1953 170B
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Jim Collins
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Re: Cruise prop T/0 vs climb prop ?

Post by Jim Collins »

Pete,
I have a cruse prop and have regretted it on numerous occasions. Like short grass strips, obstacles at the end of a runway, ect...
A climb prop or something in-between will make the airplane a little slower but might be better in all around usage.
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Richgj3
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Re: Cruise prop T/0 vs climb prop ?

Post by Richgj3 »

I have a 76/54 on my 170B. I’m at sea level and I won’t go out of less than 2500 feet of grass with two people and full tanks. ROC is 500-800 rpm depending on the day ONCE YOU GET AIRBORNE. Acceleration is anemic. But it does a true 120 mph.

I’d like to find a 76/51.

As far as altitude goes I’ve only been to 9.5 since I’ve owned it. Not a problem.

Rich
Rich Giannotti CFI-A. CFI-I SE.
1952 C170B
N2444D s/n 20596
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Bruce Fenstermacher
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Re: Cruise prop T/0 vs climb prop ?

Post by Bruce Fenstermacher »

Pete I seem to recall that with the Cal Twist 172MDM, 56 pitch is cruise. So at 55 pitch you have a sorta cruise prop not full cruise. So you have that going for you. :D

I think George may have the same prop you do and can chime in
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GAHorn
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Re: Cruise prop T/0 vs climb prop ?

Post by GAHorn »

Richgj3 wrote:I have a 76/54 on my 170B. I’m at sea level and I won’t go out of less than 2500 feet of grass with two people and full tanks. ROC is 500-800 rpm depending on the day ONCE YOU GET AIRBORNE. Acceleration is anemic. But it does a true 120 mph.

I’d like to find a 76/51.

As far as altitude goes I’ve only been to 9.5 since I’ve owned it. Not a problem.

Rich
I have JUST WHAT YOU WANT..if you have a six-bolt crank. I have a once-overhauled, 600 hour TT EM7651 which I plan to either re-pitch to 73 or to trade for one similar condition.
Bruce Fenstermacher wrote:Pete I seem to recall that with the Cal Twist 172MDM, 56 pitch is cruise. So at 55 pitch you have a sorta cruise prop not full cruise. So you have that going for you. :D

I think George may have the same prop you do and can chime in
Correct, I have an EM7655 and I want to know what time of year you plan to make that trip, Pete?

It was a formation flight from Texas to Las Vegas, Convention 2002:
Jamie and I, full fuel, and X-amount lbs of bags (gross wt at least) left a June 2002 Winslow AZ Rwy 29 at 2PM…(Elev. 4951)….and used the MOST of the 7001’ …only to find ourselves viewing cactus, agarita, and ocotillo-thorns up close for the next mile or so. We spent the better part of an hour getting to 11,500 MSL and then fought updrafts and downdrafts which saw 9K and 12.5K for an hour or two on the way to Las Vegas listening to Cleo Bickford laughing us over the radio while he did the same in Wendell Wybornys’ standard B-model with a DM7653.

Wendells airplane would leave the ground 500’ or less sooner than we would…and a cruise climb indicating around 85-90 his ‘54 model would pull slightly ahead…by the time we reached cruising altitude of 8500 out of Ruidoso…. they were about 3 miles ahead of us… Over the next hour we’d catch up and pass them and after another hour and a half we’d still run 2450 RPM and Cleo would run 2550 to stay in formation.
But that high density altitude takeoffs and climbs were concerning.
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'53 B-model N146YS SN:25713
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Richgj3
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Re: Cruise prop T/0 vs climb prop ?

Post by Richgj3 »

George

Thanks for the offer but I have an 8 bolt crank.

Rich
Rich Giannotti CFI-A. CFI-I SE.
1952 C170B
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pdb
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Re: Cruise prop T/0 vs climb prop ?

Post by pdb »

George,

I will be heading east from Eastern Oregon in Mid July so it will be hot and high density altitudes crossing the Rockies. I am concerned that I am going to have to fly fast to achieve the max rpm’s that will be available at those altitudes and temperature. The potential speed savings could really help on a long trip but may provide more excitement that I am up for. At home, my local field elevation is about 140’, a hot day in summer is 70, and I am using my 80/42 climb prop.

I have made the trip to the East Coast several times before but usually with a compromise cruise climb prop. The new prop is going to take some getting used to. I think I am going to avoid Wyoming.

All the comments are much appreciated. Thank you all.
Pete Brown
Anchorage, Alaska
N4563C 1953 170B
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GAHorn
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Re: Cruise prop T/0 vs climb prop ?

Post by GAHorn »

One thing that might alleviate some concerns about climb props (or props believed to be too finely-pitched for cruise) is that this engine is not harmed by cruising above the usual recommended 2450 RPM.

These O-300 and C-145 engines share most components (rods, most bearings, accys, cylinders, pistons, etc) with the GO-300 which was rated to run at 3200 RPM for takeoff and cruise around all day at 3000 RPM. So if you need to speed-up with a “flat pitched” prop…. run it at higher RPM…. It will not harm the engine, it will only consume a little bit more fuel.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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cessna170bdriver
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Re: Cruise prop T/0 vs climb prop ?

Post by cessna170bdriver »

pdb wrote:... I think I am going to avoid Wyoming.
Eastbound the winds might allow you to overfly Wyoming without a fuel stop, but if you do land in Wyoming try to use Rock Springs (KRKS); it has a 10,000’ runway slightly downhill to the west with no obstacles and a steep drop off the end. Going home to California from the 2010 170 convention in Michigan, we made it to Scottsbluff, NE the first day. With westerly winds, making Utah without a fuel stop was iffy at best so I chose to refuel at RKS. I had my wife, luggage, and about 75 lb of my late father’s tools on board so I only partially fueled to about 2000lb gross weight. It was noonish and about 80F at departure. Just after I leaned for highest RPM and lined up on the runway I heard “Density altitude 9500 feet” broadcast on Unicom. The roll was 3-4000 feet, and about that much more accelerating in ground effect to best ROC. I think we crossed the end at about 50-100’ AGL, but it was clear sailing from there. This was with a standard pitch McCauley 7653 prop.
Miles

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GAHorn
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Re: Cruise prop T/0 vs climb prop ?

Post by GAHorn »

cessna170bdriver wrote:
pdb wrote:... I think I am going to avoid Wyoming.
Eastbound the winds might allow you to overfly Wyoming without a fuel stop, but if you do land in Wyoming try to use Rock Springs (KRKS); it has a 10,000’ runway slightly downhill to the west with no obstacles and a steep drop off the end. Going home to California from the 2010 170 convention in Michigan, we made it to Scottsbluff, NE the first day. With westerly winds, making Utah without a fuel stop was iffy at best so I chose to refuel at RKS. I had my wife, luggage, and about 75 lb of my late father’s tools on board so I only partially fueled to about 2000lb gross weight. It was noonish and about 80F at departure. Just after I leaned for highest RPM and lined up on the runway I heard “Density altitude 9500 feet” broadcast on Unicom. The roll was 3-4000 feet, and about that much more accelerating in ground effect to best ROC. I think we crossed the end at about 50-100’ AGL, but it was clear sailing from there. This was with a standard pitch McCauley 7653 prop.
That takeoff description reminds me of the time (1971) I watched a L-1049 Constellation freighter with 30,000 lbs of oilfield pipe take off from Houston Hobby Rwy 12 headed for So. America. After observing it pull full power before releasing the brakes… it rolled and rolled and….rolled… and the nose wheel lifted about a foot and the mains remained stuck to the pavement until they went off the far-end …. the airplane remained in ground effect until houses became obstacles then it raised the gear…. and we watched it for about 10 minutes as it got smaller and smaller ….until as a “dot” it disappeared over the horizon like a ship-at-sea…. and one of the old-timers remarked that …“it only flew due to curvature-of-the-earth”… 8O

A fellow named Jack Strickland was the co-pilot on that thing and when they returned the next week he said that they were so inebriated with adrenalin on that takeoff they almost forgot to switch tanks! (Typically they would fill the main tanks with 130/145 octane and all the others with 100/115 and after raising the gear and reducing throttles to METO they’d switch from mains to aux tanks to conserve the 130/145 for takeoffs because it was getting difficult to buy at most airports. He said they were over the Gulf of Mexico before the checklists reminded them to switch tanks. :lol:
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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bgiesbrecht
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Re: Cruise prop T/0 vs climb prop ?

Post by bgiesbrecht »

I'd keep the 8042 on and enjoy the scenery. 55 prop is gonna be anemic at altitude in summer, you'll pretty much be forced to depart early mornings / evenings if you're full of gas and another pax.
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n2582d
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Re: Cruise prop T/0 vs climb prop ?

Post by n2582d »

… That takeoff description reminds me of the time (1971) I watched a L-1011 Constellation freighter … .
George, looks like you may be conflating two Lockheed transports, the L-1049 and the L-1011. The L-1049 Constellations became known as “the world’s best tri-motors” in their latter years. The L-1011, of course, was the TriStar. Dynamic Aviation, a company I used to work for, is restoring the first Air Force One, Eisenhower’s Connie. I can’t imagine what that’s costing. No wonder I was making peanuts working for them!
Gary
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Re: Cruise prop T/0 vs climb prop ?

Post by GAHorn »

n2582d wrote:
… That takeoff description reminds me of the time (1971) I watched a L-1011 Constellation freighter … .
George, looks like you may be conflating two Lockheed transports, the L-1049 and the L-1011. The L-1049 Constellations became known as “the world’s best tri-motors” in their latter years. The L-1011, of course, was the TriStar. Dynamic Aviation, a company I used to work for, is restoring the first Air Force One, Eisenhower’s Connie. I can’t imagine what that’s costing. No wonder I was making peanuts working for them!
I guess I had a bran pharrtt. Yep… sure did! Thx. (for correctness I’ll edit that one)…LOL

I actually got to sit at the Engineers station on that airplane the day before that flight as they prepared it. They’d just installed new spark plugs and needed to make a full-power run-up. I can remember the dang thing had oscilloscopes that displayed each spark plug (total of 36 each engine) as it fired on a graphic display. The engineer explained to me that for takeoff the captain would call for “thirty-inches” and he’d run the throttles up to that manifold pressure for about 15 seconds …and only THEN would the captain call for take-off power….. which was determined by density altitude and takeoff weight vs runway… but could be up to 75-inches of MP. 8O The reason for the 30” was to pre-heat up the spark plugs…otherwise a power advance from idle to takeoff power would burn them up. It was quite an experience for a 23 year old new CFI to watch that runup! (They did one engine at a time to save the tires/brakes on the as-yet unloaded airplane. It took them all night to load the pipe cargo.)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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