Twenty years of reengined tug

[Exadios]

There's an interesting article in the September / October, 2011, edition of "Gliding International" about Kingaroy Gliding Club's V8 Pawnee tug.

 

The old Ford V6 has been removed and replaced with a GM 5.7 liter V8. As installed the engine develops 280 hp at maximum engine RPM of 4500. GM's specifications for the engine are: max. power 350 hp at 5400 RPM (red line is at 6000 RPM). So the engine is derated for use in the tug.

 

The engine drives a three bladed prop via a 2:1 reduction drive.

 

Climb out is typically at 4250 RPM which yeilds a climb rate of 600' / min. for the tug glider combination.

 

 

 

 

[JimG]

Good Plan, does the article mention or does anyone know what the PSRU they use with the LS-1 .

 

JimG

 

 

[facthunter]

I reckon they might be onto something there. I would be interested in what reduction set-up is used, too, Nev

 

 

[Exadios]

Good Plan, does the article mention or does anyone know what the PSRU they use with the LS-1 .JimG

The article does not say but I seem to remember hearing that it was engineered and manufactured as a one off in the 1990s. I seem to remember that this was a major problem then but I cannot remember the details.

 

If you are interested I'm sure that if you write the club they will give you details.

 

 

[Guest rocketdriver]

The article does not say but I seem to remember hearing that it was engineered and manufactured as a one off in the 1990s. I seem to remember that this was a major problem then but I cannot remember the details.If you are interested I'm sure that if you write the club they will give you details.

I think the GCV at Benalla was talking about auto engine conversions for their Pawnees, but they eventually decided(I think) that the power claimed was exagerated and that the good old flat 6 we were already using was the way to go .... 265 hp if I think. At the time we were plagued with constant cylinder cracking no matter what descent regime was adopted. The problem was "cured" or at least diminished when we stopped using refurbished pots, If I remember correctly ....

I can't remember the normal climb rate, but I do recall , with selected glider pilots, thermalling the combination using the rate of climb indicator plus seat of the pants and often seeing well over 1000ft per minute climb ..... even with a glider loaded with water ......

 

cheers

 

RD

 

 

[Exadios]

I think the GCV at Benalla was talking about auto engine conversions for their Pawnees, but they eventually decided(I think) that the power claimed was exagerated and that the good old flat 6 we were already using was the way to go .... 265 hp if I think. At the time we were plagued with constant cylinder cracking no matter what descent regime was adopted. The problem was "cured" or at least diminished when we stopped using refurbished pots, If I remember correctly ....I can't remember the normal climb rate, but I do recall , with selected glider pilots, thermalling the combination using the rate of climb indicator plus seat of the pants and often seeing well over 1000ft per minute climb ..... even with a glider loaded with water ......

 

cheers

 

RD

My understanding (which may be wrong) is that, in effect, there is allowed to be only one reengined tug in Australia. The developement at Kingaroy is the result of an agreement with CASA and the latter are not interested in allowing the other clubs to do the same.

 

If the option was avaliable to other clubs I feel sure that all three aerotow clubs here in WA would have reengined our tugs. I image the the eastern states clubs woud do the same.

 

The thing is that it only takes having to fork out $50000 for engines on a few occasions to make one think of possible alternatives.

 

The normal climb rate with a glider attached is about 600' / min. Like all clubs we too thermal the tug to get the 1000' / min that you have observed.

 

 

[kaz3g]

I think the GCV at Benalla was talking about auto engine conversions for their Pawnees, but they eventually decided(I think) that the power claimed was exagerated and that the good old flat 6 we were already using was the way to go .... 265 hp if I think. At the time we were plagued with constant cylinder cracking no matter what descent regime was adopted... RD

Hi RD

 

As I remember, those Pawnees used to come down PDQ after release, in fact one driver (and attached glider pilot) was killed when he rolled over into a steep descending turn before the glider had released. The pressure on the rings was then so great neither could release and the tug pilot couldn't recover because of the drag of the glider behind.

 

Now that was a long time ago. The Doc was CFI and Shippie was training the tuggies as commercial pilots.

 

kaz

 

 

[Guest rocketdriver]

Hi RDAs I remember, those Pawnees used to come down PDQ after release, in fact one driver (and attached glider pilot) was killed when he rolled over into a steep descending turn before the glider had released. The pressure on the rings was then so great neither could release and the tug pilot couldn't recover because of the drag of the glider behind.

 

Now that was a long time ago. The Doc was CFI and Shippie was training the tuggies as commercial pilots.

 

kaz

Hi Kaz .... Yes, I guess we did .... our job was to getum up there, flingemoff and getbackdown for the next one! A ten minute turn around was considered normal from hook up to hook up via 2,000 ft. .... Don't remember that prang either ... must have been before my time ....

I don't remember "the Doc", but Pat Chip was the local flying school (in partnership with Ed?)

 

During my time there. Pat seemed to have abit of a thing against the gliding club and I remember one time when Col Paye came in with the Spit whilst I was refuelling the tug and asked if he could use the grass on take off to save his tyres .... I said I was sure there would be no probs, just call on the CTAF freq andf let them Know ..... Pat was there and said words to the effect of "just do it .. they can get stuffed" ....

 

Ahh those were the days ...... "Carrier" landings on the tiny 8ft wide 100 m long glider take off strips that they put in after the airfield reconstruction. Talk about pressure. Everyone knew you were going for it, even on down or cross wind days, so you dared not muck it up! Trick was to touch down at absolutely minimum airspeed right at the beginning of the strip and stop before the end .... hmmmmm. (actually not sure of the dimensions of the tarmac strip. Width was just a bit more than the Pawnee's wheel track, and length??? might have been a bit less than 100 m, never measured it) And then there was landing on tow ... used to love doing that for the satisfaction of the precision flying that it required .....

 

cheers

 

RD

 

 

[Tomo]

My RAA instructor in Dalby I believe installed that 350 chev in the Pawnee, he has another complete unit in his hanger ready for installation too I think.

 

2:1 reduction drive is a belt from memory.

 

The Pawnee's we use at Jondaryan have the O-540 B2B5 Lycoming engines.

 

 

[David Isaac]

I was of the belief that there was Chev V8 powered Pawnee at Lake Keepit (Manila / Tamworth area), can anyone confirm that .

 

 

[Exadios]

I was of the belief that there was Chev V8 powered Pawnee at Lake Keepit (Manila / Tamworth area), can anyone confirm that .

Lake Keepit has a Callair. It has the original Lycoming, I believe.

 

 

[Exadios]

I was of the belief that there was Chev V8 powered Pawnee at Lake Keepit (Manila / Tamworth area), can anyone confirm that .

It seems that there was a LS1 (V8) powered tug at Lake Keepit for a while on trial a couple of years ago. It is basically the same as the Kingaroy LS1 edition I believe. It is operating under a Special Certificate of Airworthyness. There is a page at the GFA giving some running cost comparisons.

 

 

[Guest rocketdriver]

It seems that there was a LS1 (V8) powered tug at Lake Keepit for a while on trial a couple of years ago. It is basically the same as the Kingaroy LS1 edition I believe. It is operating under a Special Certificate of Airworthyness. There is a page at the GFA giving some running cost comparisons.

Interesting cost comparisons there Exadios ..... Unless the Lycoming is being overfuelled by about 20% for cooling purposes, the implication is that the LS1 is making less horsepower. I imagine that the specific consumption would not be that different ......

cheers

 

RD

 

 

[fly_tornado]

lycomings where designed when Avgas was 15c a gallon

 

 

[Guest rocketdriver]

lycomings where designed when Avgas was 15c a gallon

True, but the point I was trying to make is that each litre of fuel contains just so much energy no matter what engine burns it. The more horsepower,the engine develops, the greater the fuel use .... Whilst there is some difference in efficiency from one engine to another, I would be surprised if the Lycoming was 20% less efficient .... but possible I guess.

cheers

 

RD

 

 

[fly_tornado]

How much power was a 350' V8 producing in the 40's? Engine designers has made huge gains in efficiency, the LS1 carry 10s of millions of development that Lycoming just can't afford.

 

 

[kaz3g]

...I don't remember "the Doc", but Pat Chip was the local flying school (in partnership with Ed?) RD

The Doc was Ed McKeogh who signed me off on aerotow in an IS28 and Pat Ship got me my pilot's licence in a brand new Warrior a few years later. I did most of my gliding out of Euroa but also used Benalla and Tocumwal.

 

It was an odd partnership because, as you say, Pat was quite caustic in his remarks about the glider folk yet his close friend and partner in Skyways was Ed who was CFI of the gliding club.

 

Oh, I just remembered... Ed "endorsed" me in the Archer, too.

 

kaz

 

 

[Exadios]

True, but the point I was trying to make is that each litre of fuel contains just so much energy no matter what engine burns it. The more horsepower,the engine develops, the greater the fuel use .... Whilst there is some difference in efficiency from one engine to another, I would be surprised if the Lycoming was 20% less efficient .... but possible I guess.cheers

RD

I wouldn't be surprised at all with a 20% efficiency difference.

 

I believe that one of the tweeks is to adjust the LS1 EMS for max effeciecy at the revs used for a climb of 600' / min.

 

 

[Exadios]

How much power was a 350' V8 producing in the 40's? Engine designers has made huge gains in efficiency, the LS1 carry 10s of millions of development that Lycoming just can't afford.

One of the rationals behind put an auto engine in an aircraft is the advantages given by higher manufacturing production volumes - the sharing of design costs over a larger market and, from the GFA figures and the article, the increased reliability. The problem with the Ly is that they are just soo unreliable.

 

I notice that the GFA uses the Lycoming's rated life of 2000 hours. However, I don't believe that any of the gliding clubs have got this sort of life out of an engine.

 

 

[fly_tornado]

Lycomings weren't designed for a lot of stop start flying, that alloy must get brittle pretty quickly. Water cooling is 10x more efficient than air cooling. I can't understand why CASA is so against auto engines.

 

 

[David Isaac]

Water cooling is 10x more efficient than air cooling.

It is certainly more efficient, but there is always a weight penalty with water cooling.

 

I can't understand why CASA is so against auto engines.

Because they were not designed for constant WOT applications which reduces the engine life. I am curious as to the real TBO of the ali Chev motor.

[Exadios]

It is certainly more efficient, but there is always a weight penalty with water cooling.Because they were not designed for constant WOT applications which reduces the engine life. I am curious as to the real TBO of the ali Chev motor.

According to the article the weight penalty of the LS1 over the Ly is 20Kg. I assume that they are including the weight of the radiator and coolant, etc, in that comparison.

 

The LS1 is not run at anywhere near its maximum which is 350 hp at 5400 RPM. When installed WOT is 280 hp at 4500 RPM. The agreement between CASA and the owners Pawnee for the original Ford V6 implementation was 1000 hours. I don't know if that carries forward for the LS1 but, even if it does, the cost of the latter makes it very much cheaper than the Ly at 2000 hours. Of course the real life of an Ly is closer to 1000 hours than 2000 hours.

 

 

[fly_tornado]

The problem with aero engines is that they can't survive without lead, which nearly all auto engines are now capable of doing. The advent of smarter ECUs fixes a lot of the issues with auto conversions, the issue of running @ 75% power for extended periods doesn't seem impossible, especially if you tune the engine for lower rpms.

 

The main advantage with auto conversions is you don't need to work to overhaul schedules, is always going to be cheaper/safer/quicker to replace the entire engine.

 

 

[facthunter]

I generally am not a fan of auto conversions, but as I have said before, I believe that this alloy pushrod V8 has potential. From 350 to 280 HP is not a big drop and I would expect some modifications to the engine to be desireable, to achieve reliability.

 

The life of a Lycoming in Tug or Para drops is not very long. The biggest problem is head cracking because of thermal shock, so the period between cylinder changes may be quite short, and it's expensive. Modification of handling technique may help but the situation demands quick times or the customer is not happy. The pawnee is heavier than a tug needs to be and they are all pretty old..

 

A Pilatus Porter ( Pt-6 engine) would have to be a good jump ship wouldn't it? . Suppose it's too dear. Nev

 

 

[Exadios]

I generally am not a fan of auto conversions, but as I have said before, I believe that this alloy pushrod V8 has potential. From 350 to 280 HP is not a big drop and I would expect some modifications to the engine to be desireable, to achieve reliability.The life of a Lycoming in Tug or Para drops is not very long. The biggest problem is head cracking because of thermal shock, so the period between cylinder changes may be quite short, and it's expensive. Modification of handling technique may help but the situation demands quick times or the customer is not happy. The pawnee is heavier than a tug needs to be and they are all pretty old..

A Pilatus Porter ( Pt-6 engine) would have to be a good jump ship wouldn't it? . Suppose it's too dear. Nev

The climb out, at 600' / min, is done at 4250 RPM and 250 hp. The engine load is not excessive.

 

I think most of the Ly failures I've seen are because of metal in the oil at about 1300 hours.