Stranded - AOG

weirdjim said:
I was taught that a boxer engine (so named by Hitler) had both pistons on one side coming up together and then both pistons on the other side coming up together. As I vaguely remember it, it makes the design of an "interference free" engine easier. I've never seen an aircraft engine like that.
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That's not what I was taught. I was told that it was the term for opposed engines that have the pistons in the cylinders that are opposite each other travelling inward toward the center at the same time as each other and then outward at the same time as each other. The "boxer" reference was from the similarity of the pistons' motions to the act of a boxer punching his fists together.

These engines would have the inertial forces balanced by the opposing cylinder, and the firing would be even at 360 degree spacing for a 4-cycle and simultaneous for 2-cycle.

Having all of the pistons on one side coming in while all of them on the other were going out would double up on the inertial forces, and would be very difficult to balance (balance shafts and such), and would be brutal on the main bearings. These would have two rods per journal, like so many V-configuration engines, and all of the journals in line with each other. The timing on an opposed pair would be 540 degrees and then 180 degrees, so even-firing would only be possible in configurations with multiples of four cylinders (no two or six cylinder option).

I realize that my discussion of the shortcomings of such an engine have nothing to do with the name of that engine, but think about it for a minute. How would the name of such an ungainly contraption, few examples of which have been attempted, gotten so ingrained into the popular lexicon?

EDIT: I took your advice to read the "true-boxer" info, and was expecting to come back with a "Well, I'll be damned, whooda thunkit" retraction to the above, but was pleasantly surprised to see that I was not wrong.

Please re-read it more carefully, and you will find that it supports the assertion that every opposed aircraft engine in the group that you think of as "standard" or "normal", is in fact a "boxer". The fact that aviation professionals prefer to use another term that is a better fit within the group of terms that are used to describe other engines ("O", "I", "R", "V") doesn't refute that.
 
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weirdjim said:
.....
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Would be appreciated to show me why aviation engines aren't considered in the boxer class of engines. Benz did invent the first horizontally opposed engine. The whole premise behind a boxer engine is that pairs of pistons are in sync in that they both reach BDC and TDC at the same time. I did concede the point that we don't call them that, but boxer engine, flat engine, and horizontally opposed are generally considered synonymous as far as I know.

Now, I've heard arguments saying a boxer and some other type (180 degree engine, flat four engine, etc) are a little different. I feel like this differentiation that people make aren't really respected in the engineering world. Boxer engines work like our aviation engines do now, with each pair of pistons, front and back, reaching BDC and TDC together. The differentiation people are trying to make is that in some designs, one back engine, and one front engine, reach TDC or BDC, but this is a horribly unbalanced engine design with less than 6 cylinders, and that is what Karl Benz was addressing with respect to having two opposed cylinder's pistons moving together. One front and one back, for example, are not opposing cylinders.

In fact, even "true boxer" as defined by the wiki page IS REFERRING TO THE EXACT DESIGN OF AVIATION ENGINES, and provides a picture right there on the right side of the page.

Now, if you are saying they were having one set of cylinders on the right side move up together, while the left moves down together, that would be truly a terrible engine design. It would shake itself apart from the dynamic forces.

Here's a boxer engine description from a Subaru dealer, including an animation: http://www.manchestersubaru.com/subaru-boxer-engine.htm

Here's a suburu UK video: https://www.youtube.com/watch?v=mqX0DQ5L3ds

As for a certificated aircraft, here's a Tecnam P2006T, which is a standard certificated aircraft, with type certificated engines, the 912S. 912S' (not to be confused with the 912iS) is a FAR 33 type certificated engine. The same applies to the S engine, don't turn it backwards.

To be honest, you're just being excessively pedantic.
 
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nrpetersen said:
The reason to not turn an engine (with accessories) backwards is that it may break the vacuum pump vanes, particularly the carbon ones.
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In the shop we turn engines backwards all the time and never harm the vacuum pumps. If they break, it's because the vanes were worn far past their limits and got cocked in the rotor slot and jammed. Better to have it fail on the ground.

Engines often rock backward a blade or so on shutdown or a failed start.
 
engine-flat-4.gif


http://auto.howstuffworks.com/question366.htm
 
Stevel said:
That's not what I was taught. I was told that it was the term for opposed engines that have the pistons in the cylinders that are opposite each other travelling inward toward the center at the same time as each other and then outward at the same time as each other. The "boxer" reference was from the similarity of the pistons' motions to the act of a boxer punching his fists together.

These engines would have the inertial forces balanced by the opposing cylinder, and the firing would be even at 360 degree spacing for a 4-cycle and simultaneous for 2-cycle.

Having all of the pistons on one side coming in while all of them on the other were going out would double up on the inertial forces, and would be very difficult to balance (balance shafts and such), and would be brutal on the main bearings. These would have two rods per journal, like so many V-configuration engines, and all of the journals in line with each other. The timing on an opposed pair would be 540 degrees and then 180 degrees, so even-firing would only be possible in configurations with multiples of four cylinders (no two or six cylinder option).

I realize that my discussion of the shortcomings of such an engine have nothing to do with the name of that engine, but think about it for a minute. How would the name of such an ungainly contraption, few examples of which have been attempted, gotten so ingrained into the popular lexicon?

EDIT: I took your advice to read the "true-boxer" info, and was expecting to come back with a "Well, I'll be damned, whooda thunkit" retraction to the above, but was pleasantly surprised to see that I was not wrong.

Please re-read it more carefully, and you will find that it supports the assertion that every opposed aircraft engine in the group that you think of as "standard" or "normal", is in fact a "boxer". The fact that aviation professionals prefer to use another term that is a better fit within the group of terms that are used to describe other engines ("O", "I", "R", "V") doesn't refute that.
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Those are "opposed piston" engines and the only ones I know of are all 2 strokes like the Jumo 205. They are very good engines that are expensive to build.

"Boxer" refers to Benz's "contra engine" design we are familiar with in VWs, planes, and few others.
 
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Engine fun time :D

This is an opposed PISTON engine: http://www.mekanizmalar.com/xtwo_crank_opposed_piston_engine_large.jpg.pagespeed.ic.UtlRMhojqw.jpg

Another example: http://www.mekanizmalar.com/xone_crank_opposed_piston_engine_large.jpg.pagespeed.ic.ufI9qjAUjB.jpg

I never seen this version... neat: http://www.pattakon.com/patpoc/PatPOC_small2.gif

Wiki page: https://en.wikipedia.org/wiki/Opposed-piston_engine



This is an opposed CYLINDER/flat/boxer engine (2 cylinder, TRUE boxer configuration if the wikipedia page is correct on the definition): http://bookdome.com/science/New-Art-Flying/images/Engine-with-horizontally-opposed-cylinders-1.jpg

Another "true boxer": http://www.kfz-tech.de/Bilder/Kfz-Technik/Hubkolbenmotor/ZweiZylB01.gif

Another opposed cylinder engine, 4 cylinders, but would not qualify as a "true boxer" since two rods are connected to the same crank pins and would be unbalanced as hell: http://www.sweethaven02.com/MechTech/Auto03/item0115.gif



Here's an opposed cylinder, opposed piston engine to really throw a wrench in the works!

https://www.youtube.com/watch?v=5Y8QqeuvArE

Animated GIF of OPOC: http://www.ecomotors.com/sites/default/files/twostroke-loop.gif
 
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Henning said:
Those are "opposed piston" engines and the only ones I know of are all 2 strokes like the Jumo 205. They are very good engines that are expensive to build.

"Boxer" refers to Benz's "contra engine" design we are familiar with in VWs, planes, and few others.
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I think you are mis-reading my description. I was attempting to describe the Benz engine, but didn't think to use TDC and BDC simultaneously as the method to describe the motion of the pistons.

Edit: Dan Thomas' animation post is an example of what I know as a "boxer", and can be configured in as many pairs of cylinders as you like until you reach the practical limit of the crankshaft's ability to hold together. Six cylinders seems to be comfortably under that limit, and, based on what auto-makers have chosen to do, eight seems to be sketchy at best, since most horizontally opposed eights are of the 2 rods per pin persuasion.
 
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txflyer;1852569 said:
Just treat every prop like it's going to fire if you turn it and you'll be covered. I never turn mine backwards although the debate about it is questionable as to whether it hurts or not, so I just don't do it.

Stand flat footed facing the prop with a good stance so you don't lose your footing. You put most props at the ten-oclock position, and just put your fingers over the trailing edge of the prop to the first digit on your fingers. Don't grip the prop. Pull down and as your pulling down step back and keep stepping back.
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Even though I know conceptually how to hand prop, I wouldn't want to do it the first time without someone next to me walking me through the process, in addition to the person inside the plane. I do wish I was shown how to hand prop during my private training. Kinda like a spin at this point too, conceptually I know how to recover, but I'm not going to go intentionally spin without having someone with some experience next to me.
 
Somedudeintn said:
Even though I know conceptually how to hand prop, I wouldn't want to do it the first time without someone next to me walking me through the process, in addition to the person inside the plane. I do wish I was shown how to hand prop during my private training. Kinda like a spin at this point too, conceptually I know how to recover, but I'm not going to go intentionally spin without having someone with some experience next to me.
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It never hurts to have some instruction. But you can do it easily. The demonstration at OSH was a small woman on a 172.

We make it harder than it is talking about it. Just use some common sense.

An interesting factoid from the class was that there are no FAA rules when it comes to hand propping. None.
 
Anticept said:
Engine fun time :D

This is an opposed PISTON engine: http://www.mekanizmalar.com/xtwo_crank_opposed_piston_engine_large.jpg.pagespeed.ic.UtlRMhojqw.jpg

Another example: http://www.mekanizmalar.com/xone_crank_opposed_piston_engine_large.jpg.pagespeed.ic.ufI9qjAUjB.jpg

I never seen this version... neat: http://www.pattakon.com/patpoc/PatPOC_small2.gif

Wiki page: https://en.wikipedia.org/wiki/Opposed-piston_engine



This is an opposed CYLINDER/flat/boxer engine (2 cylinder, TRUE boxer configuration if the wikipedia page is correct on the definition): http://bookdome.com/science/New-Art-Flying/images/Engine-with-horizontally-opposed-cylinders-1.jpg

Another "true boxer": http://www.kfz-tech.de/Bilder/Kfz-Technik/Hubkolbenmotor/ZweiZylB01.gif

Another opposed cylinder engine, 4 cylinders, but would not qualify as a "true boxer" since two rods are connected to the same crank pins and would be unbalanced as hell: http://www.sweethaven02.com/MechTech/Auto03/item0115.gif



Here's an opposed cylinder, opposed piston engine to really throw a wrench in the works!

https://www.youtube.com/watch?v=5Y8QqeuvArE

Animated GIF of OPOC: http://www.ecomotors.com/sites/default/files/twostroke-loop.gif
Click to expand...

I like that OPOC engine.
 
txflyer said:
An interesting factoid from the class was that there are no FAA rules when it comes to hand propping. None.
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In Canada we have this:

Starting and Ground Running of Aircraft Engines


  • 602.10 (1) No person shall start an engine of an aircraft unless
    • (a) a pilot’s seat is occupied by a person who is competent to control the aircraft;
    • (b) precautions have been taken to prevent the aircraft from moving; or
    • (c) in the case of a seaplane, the aircraft is in a location from which any movement of the aircraft will not endanger persons or property.
  • (2) No person shall leave an engine of an aircraft running unless
    • (a) a pilot’s seat is occupied by a person who is competent to control the aircraft; or
    • (b) where no persons are on board the aircraft,
      • (i) precautions have been taken to prevent the aircraft from moving, and
      • (ii) the aircraft is not left unattended.
I'd bet the FARs might have something similar.
 
Dan Thomas said:
In Canada we have this:

Starting and Ground Running of Aircraft Engines


  • 602.10 (1) No person shall start an engine of an aircraft unless
    • (a) a pilot’s seat is occupied by a person who is competent to control the aircraft;
    • (b) precautions have been taken to prevent the aircraft from moving; or
    • (c) in the case of a seaplane, the aircraft is in a location from which any movement of the aircraft will not endanger persons or property.
  • (2) No person shall leave an engine of an aircraft running unless
    • (a) a pilot’s seat is occupied by a person who is competent to control the aircraft; or
    • (b) where no persons are on board the aircraft,
      • (i) precautions have been taken to prevent the aircraft from moving, and
      • (ii) the aircraft is not left unattended.
I'd bet the FARs might have something similar.
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According to the guy at Osh, there is no FAA rule or rules for hand propping an aircraft in the United States.

And that's a good thing. We don't need more rules. :wink2:
 
Dan Thomas said:
engine-flat-4.gif


http://auto.howstuffworks.com/question366.htm
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This is not exactly our opposed 4 cyl Lycoming or Continental engine however. In aircraft engines the cylinders are interleaved such that the right cylinders are longitudinally displaced from the left side pair. In the model above they are not. This is probably done to minimize engine length.

This necessary L vs R offset is an important limitation for our 4 cyl opposed engines, because it creates a strong second harmonic (twice crankshaft speed) torsional vibration about a vertical axis through the engine's center of gravity, due to the short length of all the connecting rods.

That's why front and rear mounted accessories are exposed to a lot of transverse vibration, to the detriment of their mounting bracketry. Which is why Lycoming alternator mounts crack so frequently.

I think I'm right on this.....:confused:
 
nrpetersen said:
This is not exactly our opposed 4 cyl Lycoming or Continental engine however. In aircraft engines the cylinders are interleaved such that the right cylinders are longitudinally displaced from the left side pair. In the model above they are not. This is probably done to minimize engine length.

This necessary L vs R offset is an important limitation for our 4 cyl opposed engines, because it creates a strong second harmonic (twice crankshaft speed) torsional vibration about a vertical axis through the engine's center of gravity, due to the short length of all the connecting rods.

That's why front and rear mounted accessories are exposed to a lot of transverse vibration, to the detriment of their mounting bracketry. Which is why Lycoming alternator mounts crack so frequently.

I think I'm right on this.....:confused:
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That animation is of the offset engine just like an aircraft engine. The con rods on their own journals make it so.

Larger engines have crankshaft counterbalances that, among other things, control the shake about the vertical axis. Lyc alternator brackets do crack sometimes, but it's both vibration and the stresses set up in the bracket when it's bent. That bracket is too thick to be bent to such a tight radius without starting microscopic cracks. Sometimes they crack through the case bolt holes. I think they're heat-treated and sometimes not sufficiently tempered after hardening.
 
Stevel said:
Six cylinders seems to be comfortably under that limit, and, based on what auto-makers have chosen to do, eight seems to be sketchy at best, since most horizontally opposed eights are of the 2 rods per pin persuasion.
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Lycoming IO-720:

engines%5Ecertified%5E720-engine-mid.png


400 hp. Same offset cylinder idea as the fours and sixes.

hr2pfm1tz830mgetkvpk.jpg
 
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Thanks for your input, problem identified. At rest the battery was reading 12 volts. With a load, 4 volts. My mechanic said "That ain't gonna cut it."

I got the needed jump, monitored my voltage on my GPS and Ammeter, followed Doc Mirror's directions on testing/running/charging, etc., and safely delivered 77R back home. New battery will be on order tomorrow.

Interestingly, for those who may still be following along, as I reduced power to land and added progressively more flaps, I was unknowingly drawing down what little reserve I had created in the battery. As I raised the flaps, the radios died. Unable to talk to Ground, I sat idling clear of the runway. Eventually the tower flashed me the light gun cleared to taxi.

As I increased power and taxied, I tried the avionics master and the radios came alive again. I understand the symptoms as presented, and it confirms the battery is toast. After all this discussion, I'm also going to order new solenoids (Master & Starter) from Skytech. I like new parts on old airplanes.
 
txflyer said:
According to the guy at Osh, there is no FAA rule or rules for hand propping an aircraft in the United States.

And that's a good thing. We don't need more rules. :wink2:
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There isn't a regulatory rule, but it is in the AIM. Not enforceable directly, but I'm sure people love to see guys hand propping planes without someone inside to shut down in case something goes wrong.
 
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Anticept said:
There isn't a regulatory rule, but it is in the AIM. Not enforceable directly, but I'm sure people love to see guys hand propping planes without someone inside to shut down in case something goes wrong.
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These days, it's more typical than not to see hand prop planes be a solo operation with the tail tied and the wheels chocked. These days there are so few people who will prop you up, it's almost a necessity if you're going to operate a plane with no electrical system.
 
weirdjim said:
And you believe this why?

Jim
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Because every now and then a worn out pump will chatter and jam a blade due to the angle they are set at and break it. It's how you try to get your A&P to buy you a new vacuum pump.:rolleyes:
 
weirdjim said:
And you believe this why?

Jim
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The vanes of an (Airborne 211 series?) vacuum pump are not pure radial vanes. They are canted so they minimize any wedging effect - if they are turning the correct direction. Go the opposite direction though and they can self wedge and break the vane or the rotor.

Henning has it correct above though that it is only seriously worn pumps that will tend to do this.
 
Dan Thomas said:
That animation is of the offset engine just like an aircraft engine. The con rods on their own journals make it so.
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Your graphic model though has the spacing between the cylinders close together on one side, and far apart on the other. This would have the advantage of cancelling out the second harmonic yaw motion. The disadvantage is that it makes the engine longer so I guess that's why it isn't done this way.

Our engines have equal left and right side longitudinal spacing at the expense of introducing second harmonic yaw vibration.

I starred at it quite a while before reaching that conclusion. It is kinda hard to see.
 
iflyvfr said:
After all this discussion, I'm also going to order new solenoids (Master & Starter) from Skytech. I like new parts on old airplanes.
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Which type of master re-lay do you have? Show us a picture if you can.
 
Dan Thomas said:
Lycoming IO-720:



400 hp. Same offset cylinder idea as the fours and sixes.
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Had one of those on my brave. It was a ***** to hand prop, did it once and i was darn near too tired to climb into the cockpit after.

generally, i think the problem with hand propping is not teaching someone how to start the engine, that is pretty easy. it's distilling enough mechanical know-how so that they they can determine whether or not they have a continental starter adapter to worry about, whether their lycoming style starter is stuck engaged, whether it's a good idea to turn on the master and alternator after start, etc. Many pilots don't know enough about their systems for me to be comfortable teaching them how to start the engine.

i fully expect my kids to learn how to safely hand-prop. By the same token I completely understand jesse's sentiment about his renters not being allowed to do anything not in the normal procedures list.
 
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JHW said:
Had one of those on my brave. It was a ***** to hand prop, did it once and i was darn near too tired to climb into the cockpit after.

generally, i think the problem with hand propping is not teaching someone how to start the engine, that is pretty easy. it's distilling enough mechanical know-how so that they they can determine whether or not they have a continental starter adapter to worry about, whether their lycoming style starter is stuck engaged, whether it's a good idea to turn on the master and alternator after start, etc. Many pilots don't know enough about their systems for me to be comfortable teaching them how to start the engine.

i fully expect my kids to learn how to safely hand-prop. By the same token I completely understand jesse's sentiment about his renters not being allowed to do anything not in the normal procedures list.
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Renters have no reason to be propping up unless they are renting something with no electric system. It's not difficult, but even done properly is not completely risk free. Jesse even watched me prop up a Cherokee, the easiest start I ever pulled at that. Fired in the first tug.
 
Anticept said:
There isn't a regulatory rule, but it is in the AIM. Not enforceable directly, but I'm sure people love to see guys hand propping planes without someone inside to shut down in case something goes wrong.
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In that case, the instructor recommended you hand prop with the fuel selector off after you've turned it on and have everything ready and primed.

There's enough fuel in the gascolator/bowl to run most aircraft about thirty seconds to a minute. Logic is if the plane gets away from you, it will die soon.

The AIM you're referring to I think just says 'a competant person' should be on board. But it is not an enforceable FAA rule as you stated.
 
nrpetersen said:
Your graphic model though has the spacing between the cylinders close together on one side, and far apart on the other. This would have the advantage of cancelling out the second harmonic yaw motion. The disadvantage is that it makes the engine longer so I guess that's why it isn't done this way.

Our engines have equal left and right side longitudinal spacing at the expense of introducing second harmonic yaw vibration.

I starred at it quite a while before reaching that conclusion. It is kinda hard to see.
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I had another look at it and you're right. I think maybe the artist screwed up.
 
weirdjim said:
Second, if he got his certificate without being taught how to handprop an airplane, then I'd suggest he go get some of his money back from his instructor and spend it on training.
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Plenty of people (myself included) were taught how, and haven't had to do it in over 20 years.

Currency probably counts for something in that game. I'm not hand-propping a damn thing unless I'm stuck somewhere that I will freeze to death and have to.

Here's some fun trivia and one Jim will like.

Look at the schematic for the 172 and 182 "external power port" sometime and tell me what truly evil thing can happen when you plug in ground power...

Secondary trivia: Why doesn't plugging in ground power charge the battery?

:) ;)
 
denverpilot said:
.

Look at the schematic for the 172 and 182 "external power port" sometime and tell me what truly evil thing can happen when you plug in ground power...

Secondary trivia: Why doesn't plugging in ground power charge the battery?

:) ;)
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Well, post what you think is the schematic and let us take a look at it.

Jim
 
weirdjim said:
Well, post what you think is the schematic and let us take a look at it.

Jim
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There was an AD way back when on some Cessnas (172M, 172N, 177B/RG, 180J - K etc) where plugging in ground power would activate the engine starter.


http://rgl.faa.gov/Regulatory_and_G...AB8B5C20D3FB408B86256A3400683BBE?OpenDocument


Its not required but I recommend finding a GPU and testing those ground power receptacle systems during annuals just to make sure they work as advertised. After all, they can be a life saver.

There was a Hawker 800XP I believe that was unable to start due to unbearably cold overnight temperatures a few years back and all we did was tow a diesel power cart behind a pickup out to the BFN airport to get them going.
 
bnt83 said:
There was a Hawker 800XP I believe that was unable to start due to unbearably cold overnight temperatures a few years back and all we did was tow a diesel power cart behind a pickup out to the BFN airport to get them going.
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Rather difficult to hand-prop a turbine. I have never heard of anyone succeeding.
 
I will buy anyone a case of beer that provides proof of hand propping a PT6 :)
 
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