View Full Version : MYTHBUSTERS AND UNISA SEMINOLE
Deejay 1
21st Jun 2006, 02:58
Watched the above show last night and surprised to see the shredded remains of the Seminole become an Urban Myth. Good yarn, although pretty damn stupid trying to cut metal with a chainsaw though.
The boys decided to replicate the incident, using the tail of something, and attaching a 3 bladed engine to a railway section car, which hit at approx the same speed as the Saratoga did.
My question is, and I reckon there will be a million different answers as follows:
The photo on the following http://www.casa.gov.au/fsa/2001/sep/10-13.pdf shows a distinct difference in the distance cut between each arc of the prop compared to the television show (and yes Virginia I don't believe everything I see on TV).
So the question is would a 2 blade prop cut a different distance than a 3 blade prop and would the distance be greater or smaller.
And to all the boffins who will read this, make all things equal ie idle speed, impact speed, size of props etc and don't even think about what pitch the props might have been at other than normal start procedure!
Regards
DJ1
Buster Hyman
21st Jun 2006, 04:32
Well, assuming the speed was the same (and I don't think they had that info anyway), I would imagine that a 3 bladed prop would cut in a narrower margin. More slice for the price!
Then again, I'm no expert...maybe you should ask Jack Newton!:ouch:
Deejay 1
21st Jun 2006, 06:30
Well Buster hadn't thought of asking "Lefty".
Maybe the guy on the "Who Weekly" ad might be able to provide an idea, albeit that's a DC-3.
A bit more research on their site by the way, shows an upcoming ep where they test the myths of mobile phones on aircraft systems.
Reckon that will generate some discussion and then some.
Remember you read it here first!
No Body
21st Jun 2006, 06:59
I think I remember them saying they upped the RPM to create adequate acceleration and give them the impact speed they wanted, thus creating cuts closer together than in the picture.
From memory they had originally calculated the appropriate RPM and impact speed to space the cuts correctly, but when they tried it using their railway car that RPM didn't accelerate the car to the required velocity in the distance available.
Variable pitch props are always at full fine pitch until RPMs reach the setting of the cockpit control.
If the two props are doing the same RPM and traveling forward at the same speed, the three blade prop would create three slices in the same time/distance that the two bladed prop would take to create two slices. I assume then that the slices would have to be closer together in order to fit in all those extra slices!
Buster Hyman
21st Jun 2006, 08:54
Now, if the prop n cart were on a conveyor belt....:}:ouch::suspect:
Charles Abetz
21st Jun 2006, 10:05
It actually happened as the Mythbusters guys said by hand starting the plane.
here is the story.
A doctor surgeon from Whyalla found his battery dead in his Piper Saratoga (a powerful single-engine aircraft) at Parafield Airport, South Australia, on the night of Aug. 26, 2001. He then proceeded to hand start the engine by
turning the prop. While this is actually not illegal, it should be approached with the utmost of caution and is really
only used in remote areas where there is no help or decent pub within a long walk. The pilot, by himself, did not chock the wheels or check that the handbrake was engaged …. Anyway, the engine fires up at about
2,000 rpm and the aircraft starts taxiing to the runway on its own. The only problem with that was there were
four piper warriors and a twin-engine Seminole (the sliced plane in picture) in its way. The pilot somehow managed
to avoid certain death, although this may have been the better option considering what was about to unfold.
At a steady rate of forward movement similar to a fairly upset hippo during breeding season, the Saratoga
proceeds to destroy anything in its path. With approx. 350 liters of avgas spewing out of the damaged aircraft,
the pilot must surely realize that an appropriate timely death is about to occur….The result is he lived, and the
University of Adelaide lost one plane and the use of the other four for some time to come, all because of a flat
battery and a really bad decision. The cost—$1.5 million and absolute embarrassment for the rest of the pilot’s life.
You can just imagine the pilot, after being run over by his own plane, hanging on to the tail of his aircraft trying to stop it going any further and watching in horror as it bit by bit shreds the tail of the most expensive aircraft in the vicinity and thinking any minute the engine will stop. Just when he thinks the nightmare is going to come to an end, his aircraft then makes a sharp right-hand turn and without conscience heads to the second-most expensive aircraft in its way.
Hope you like the answer.
That seminole has some bad luck, also known as VH-MPC this seminole not only was the recipeint of the slice at Parafeild, but also this year the recipient of a chop at YSBK when a lancair came down and took out the seminoles nose wheel causing it fall on its props.:\
That seminole has some bad luck, also known as VH-MPC this seminole not only was the recipeint of the slice at Parafeild, but also this year the recipient of a chop at YSBK when a lancair came down and took out the seminoles nose wheel causing it fall on its props.:\
Surely you're not suggesting it was repaired after the Parafield incident and lived on at Bankstown???
Charles Abetz
21st Jun 2006, 21:13
You have missed the context, he means the type of plane has bad luck;)
No No i do mean the actual plane. To the best of my knowledge it is/was the same aircraft. Allways had difficulft w&b problems/limitations.... :hmm:
tlf
Qantas have some expertise in rebuilding the condemned.
Perhaps their guys had a bit of spare time after their sojorn in BKK.
Must keep the rebuild skills sharp. One never knows when that call will come.
Maui
tubby one
24th Jun 2006, 05:20
Charles Abetz - just to get the record straight
as it bit by bit shreds the tail of the most expensive aircraft in the vicinity and thinking any minute the engine will stop. Just when he thinks the nightmare is going to come to an end, his aircraft then makes a sharp right-hand turn and without conscience heads to the second-most expensive aircraft in its way.
In fact the MOST expensive aircraft in the vicinity was approx $20 million worht of brand new Lear 45 parked in front of the then BAE SYSTEMS Flight Training hangar. Had the dear doctors aircraft not eaten the Seminole he stood a good chance of seeing it chomp the tail end of the Lear which had only been at Parafield a week or two at most!!!
No No i do mean the actual plane. To the best of my knowledge it is/was the same aircraft. Allways had difficulft w&b problems/limitations.... :hmm:
Even if the aircraft was repaired there's no logical reason why it would have weight and balance issues or limitations, they are just numbers.
Now if you said it flew crooked that might have some credibility.
The aircraft at PF was VH-KBZ
goatwhacker
27th Jun 2006, 00:37
Same aircraft. MCP was the one at Parafield, dunno what reg it was then though. They gave it a new tail.
TLF, true actually. Was recently informed that when they attached the new tail section to the aircraft, the engineers miscalculated the effect that it had on the C of G limitations. Turns out as far as I now know, that it is the same and has allways been the same as a normal PA44....:D
Signature
28th Jun 2006, 12:11
I understood that the 'new' MPC was born of the remaining front bits of Parafield's PA44, and a PA44 that glided into a tree after excessive flt time without refuel (At YMMB in front of then premier J Kennett at crowns' golf course just upwind of 35R).
Worked out quite well, good spar and engines UNISA, the other had good empenage and had rego. Somewhere in the middle this unlucky bastard was born. Rebuilt at MB, then relocated to BK for work with the same company...
Nothing wrong with a re-born plane...
In my opinion, the calculations would be easier assuming full power (max RPM). Slices would be much closer with a three blader. Prop blades would be on fine pitch stops until reasonably high speeds (airspeed happily alive). If you knew the spacing of the bites, and the RPM, you could then calc the the forward speed. Either way, doctors, dentists and lawyers should not be given the keys to balistic singles.
I understood that the 'new' MPC was born of the remaining front bits of Parafield's PA44, and a PA44 that glided into a tree after excessive flt time without refuel (At YMMB in front of then premier J Kennett at crowns' golf course just upwind of 35R).
Worked out quite well, good spar and engines UNISA, the other had good empenage and had rego. Somewhere in the middle this unlucky bastard was born. Rebuilt at MB, then relocated to BK for work with the same company...
Nothing wrong with a re-born plane...
In my opinion, the calculations would be easier assuming full power (max RPM). Slices would be much closer with a three blader. Prop blades would be on fine pitch stops until reasonably high speeds (airspeed happily alive). If you knew the spacing of the bites, and the RPM, you could then calc the the forward speed. Either way, doctors, dentists and lawyers should not be given the keys to balistic singles.
OK now that I can believe, left wing and nose components of KBZ used to repair MPC. That makes sense, the rest of KBZ was trash.