1969 Turbo Twin Comanche vs Turbo 1970 and 1971

[Jeff Yuksel]

After some research i find out that Turbo 69 C's are fastest Twin Comanche's ever build.
But they are also hard to come by. I came across only few of them pop's out once in a while.
On the other hand there are some Turbo 1970 and 1971 models which comes with C/R props.
I really want to get best speed out of my future Twinkie, Especially at higher altitude.

So question is how much really 1969 Turbo model can be faster then 1970 and 1971 Turbo ones?

What would you do, which model will you go for? If you were looking for speed/climb/performance. (With stock setup)

[N3322G]

Jeff,

Let me try to give you a hand.

As point of reference my mom, Marion Jayne and I raced our Twin 39 from 1970 when it was built to 1997. The events were cross country pilot-skilled events where planes were equalized with handicaps based on stock mgr specs. We did pretty well. Mom holds the record for the most cross country speed air race victories and is the only US pilot to have raced twice around the world. Together we hold the FAI Gold medal for the longest air race in history as of now anyway, 24 days around the world in the same Twin I still fly. I share that, not to boast, except about Mom, but to let you know I spent a lot of time worrying about speed in a Twin.

As they came from the factory the PA30Bs with thinner stab were faster by 1-2 kts than PA30Cs and the PA30C was faster than our PA39. I can only guess that the airflow over the fuselage had less conflict in the non-CR. Piper claimed the 39 was faster but flight tests showed that was not true.

I saw that you are out of Glendale so I get the desire to get up and out of the lower airspace and mountains. If you fly the Rockies a lot I can see where turbo would be helpful. We had a sponsor that would have turbo'd 22G for the world race. However, forever afterward, we would have been saddled with the extra maintenance that goes with turbos so we left the IO320s stock and still won - the 14K+ mountains of Iran, Japan and the Kamchatka volcanoes did give us some challenges but no worse than flying the Twin into Aspen as we used to do until the landing fees discouraged us. It just takes planning and now we go into Rifle.

This history may be of interest to you. In the 1992 world race Mom and younger sister placed second to a sharp pilot in a turbo assisted Bonanza with 100 gallon tip tanks a.k.a. Dolly Parton tanks. No fuel was allowed in the fuselage that year so the Twin only had 10 tanks and a total of 173 gallons usable. What most people find astonishing is that from Nome to Vancouver, the Bonanza went non-stop up high 20K I think and Mom and Nancy stopped for fuel in Sitka and beat the Bonanza to Vancouver. How did they do that? Well, when they stopped for fuel they realized by looking at the water that there was a tailwind down low. so they stayed on the deck and you already know the ending for that leg.

Another similar thing happened in 1994 when we had 252 gallons on board. We'd won nearly every leg by slim margins and had lost the last 2 as we departed Anchorage to Calgary. The team nipping at our heels was a GlassAirIII that had won at OSH and SnN the prior year with a retired race car driver at the controls. Now there is an aircraft with truly stellar climb performance which is a really big deal coming out of Anchorage going SE over 14ers - and their descent rate would tear the wings off the Twin. Instead of going direct where there was forecasted icing and headwinds until you crossed the Divide, we went 100 nm out of our way. We went NE and staying at 9500 where the 320s get better performance. It was a great VFR day so we could use pilotage whereas the GlassAir was mainly in the soup and had to react to heading changes where we could anticipate. Our victory margin on that leg was an unheard of 25 minutes.

So it depends upon where you anticipate flying. 80% of mountains and you can tolerate the extra turbo maintenance., I'd suggest turbos as they will make life easier. 80% non-Rockies or you don't like extra maintenance and I'd suggest N/A engines.

My 2 cents on best speed mods:
1. fuel - tip tanks, webco or phlair nacelle tanks. I do not recommend Miler wet wings as they leak and seem to produce an inordinate amount of garbage in fuel sumps
2. flight planning for tailwinds
3. good rigging
4. LoPresti engine cowls
5. K2U props (Mom did the test flights for Hartzell on those)

After that we also found some benefit, in no particular order: one-piece windshield, digital temp gauge probe under pilot window, clean waxed airplane, control surface gap seals except rudder, gear lobe fairings, flap track fairings, tight flexible baffles, . Travel light - for every 100 lbs we carried, we lost a kt.

Hope this helps a bit. Perhaps Kristin will post, she routinely flies non-stop from NoCal to various stops in mid-continent and further with a N/A Twin.

[Kristin Winter]

If Maggie didn't have boots, I would offer to run side by side with 3322G and get a comparison. I am betting with the boots that 22G is faster. Maggie, btw, is a 1969C model, normally aspirated.

First question! Why do you want a turbo. On average, for most flight lengths, a normally aspirated Twinkie will beat a turbo. Short range flights will be down low. NA is faster. Up high, turbo is faster, but you have to burn a bunch more fuel to keep the engines cool enough so you range becomes more limited.

If we were to race from the LA area to Dallas, I would beat you most of the time with the same amount of fuel as if you go high, you will end up stopping for fuel. I won't.

[N3322G]

Not many Twins are stock any more. With the extra weight of the fuel tanks, 22G would be slower than a stock 39 ... if one could be found. Maybe the speed mods would make that up, maybe not.

In 2008 when Zach organized the 50 for 50 mass flight into OSH, he wanted everyone at 120 mph and suggested that for Twins the MP would be at 17 inches. I was so excited, I ran down to Ken's office to share. Zach's Twin is turbo ... our N/A twin at 17 inches flies at 140 mph. We use it every flight for gear down speed (150 is OK for gear down, we just want to take it easy on the gear). This is just a supporting example to Kristin's observations.

[MULEFLY]

Jeff... the 69 Turbo may be faster in the books, but I guess that there are some 70 and 71s that are faster than some 69s. It is so much rigging and mods. I have a Robertson STOL 72... and even with the Robertson, I know that I am faster than some non-Robertson equipped airplanes. If a 69 Turbo is 2 to 3 knots faster.. between climb and decent you probably will be within 5 minutes for a 4 hour flight.

Jim