Aviation History and Nostalgia Whether working in aviation, retired, wannabee or just plain fascinated this forum welcomes all with a love of flight.

Wrong way round prop

Old 19th Feb 2018, 12:05
  #21 (permalink)  
Thread Starter
Join Date: Jan 2010
Location: Mighty 8th land
Age: 71
Posts: 37
Thanks for your input. I totally agree that the AB book may have some unintentional errors, bearing in mind that many Fleet Air Arm records were destroyed during the early 1950's. I just looked either side of the "possibly destroyed" aircraft to get an idea as to when they had been built and reckoned that the construction dates of some of the "possible" aircraft were post 4/5 May. X9558 was one of my suspect aircraft....
It would be nice if there was a Saunders-Roe archive somewhere!
eMACaRe is offline  
Old 19th Feb 2018, 13:40
  #22 (permalink)  
Join Date: Dec 2007
Location: Hertfordshire
Posts: 393
Originally Posted by PDR1 View Post

If you install a prop back-to-front you here a prop still thrusts in the same direction, just less efficiently. If you had one "normal" and one "reverse" prop installed you'd get about 25% net thrust, and a walrus would barely get to a fast trot with that sort of thrust.

Ahem er . .
If half the pair of props was right and the other half wrong you might have a case that the reversed one only delivered half normal thrust so 75% of expected net thrust would be more like it.
Allan Lupton is offline  
Old 19th Feb 2018, 14:03
  #23 (permalink)  
Join Date: Nov 2015
Location: Farnham, Surrey
Posts: 1,257
True, but that isn't what was suggested. The post I was responding to suggested that it was probably one RH-rotation prop and one LH-rotation prop, with the latter therefore rotating "backwards". In this situation the RH prop would develop full thrust while the other would develop ~50% thrust in the opposite direction, giving a total of 25% of the *expected* thrust.

If you had two identical RH props with one being fitted backwards then your total thrust would be in the region of ~75% of the expected value (for any given throttle setting), but while I suspect that may be what actually happened it wasn't the scenario I was responding to.

OTOH if you had one RH prop fitted correctly, and a LH prop fitted back-to-front (so that it could rotate "forwards") bothg props would produce 100% of the expected thrust but in opposite directions, giving a net thrust of zero*


* Except that they wouldn't - the rearmost prop would probably produce slightly less thrust due to operating in the wash of the prop in front of it (the amount of reduction depending largely on the rotational speed and the solidity of the props) so there would be a (very) small net positive thrust
PDR1 is online now  
Old 19th Feb 2018, 14:48
  #24 (permalink)  
Join Date: Dec 2007
Location: Hertfordshire
Posts: 393
That post you were responding to was so confused it seems to have confused me as well. Once it introduced the total red herring of fitting a Tractor prop to a Pusher installation I more or less gave up, as what this started from was simple incorrect assembly of correct props.
Allan Lupton is offline  
Old 19th Feb 2018, 15:35
  #25 (permalink)  
Join Date: Nov 2015
Location: Farnham, Surrey
Posts: 1,257
Well indeed. But I think I got what he was saying, in which case my response was correct. But it's possible that I didn't get what he was saying, in which case my response was incorrect. I think.

Nurse - I think it's past time for my blue pill...

PDR1 is online now  
Old 19th Feb 2018, 16:00
  #26 (permalink)  
Thread Starter
Join Date: Jan 2010
Location: Mighty 8th land
Age: 71
Posts: 37
Wrong way round prop

Taken from my original source:
"It was later found that one half of the four-bladed propeller had been assembled in reverse and was unnoticed at final inspection"
Does that make it any clearer....
eMACaRe is offline  
Old 19th Feb 2018, 16:23
  #27 (permalink)  
Join Date: Jul 2002
Location: Netherlands
Age: 67
Posts: 138
As I told before it IS confusing. Not only because of tractor and pusher engines, with pushers that are Yes or not modified to run in an opposite direction, with "normal" and pusher props. Add to it that English engines run the "wrong" direction as opposed to US types and we have a Babylonian confusion!

But OK having half of the blades installed wrong, is quite an achievement from Murphy... AND no one noticed....
Luckily we are some 75 years further and comparable mistakes like this are not made any more
Double Back is offline  
Old 19th Feb 2018, 16:58
  #28 (permalink)  
Join Date: Jul 2013
Location: Grimsby
Posts: 33
You might like to read this......
Variable Pitch at the Cradle of Aviation Museum
M-62A3 is offline  
Old 19th Feb 2018, 16:59
  #29 (permalink)  
Join Date: Aug 2002
Location: UK
Posts: 325
Regretably as late as the 1980s someone still managed to fit a helicopter individual tail rotor blade the wrong way round, so the trailing edge was wrongly facing the rotational airflow. The remaining blades were fortunately the right way round. The pilots were alert to the extra vibration during ground taxi before getting airborne and it didn't lead to disaster (I think). All it needed at design phase was different retaining bolt diameters; rather than the ineffective outboard/inboard label. Murphy's Law.
Attached Images
File Type: jpg
tail.jpg (67.2 KB, 30 views)
File Type: jpg
sk.jpg (77.3 KB, 28 views)
peterperfect is offline  
Old 19th Feb 2018, 17:40
  #30 (permalink)  
Join Date: Jan 2008
Location: Bolton ENGLAND
Age: 75
Posts: 908
This crash took place at the Saunders-Roe flying ground near Chertsey, Surrey on the 1st July 1942.
New one on me.....
Planemike is offline  
Old 19th Feb 2018, 18:26
  #31 (permalink)  
Join Date: Jan 2008
Location: Reading, UK
Posts: 11,590
Originally Posted by Planemike View Post
New one on me.....
SARO had a factory on what is now Weybridge Trading Estate/Business Park and flew completed aircraft from nearby Chertsey Meads.

Chertsey Meads - UK Airfield Guide
DaveReidUK is online now  
Old 9th Mar 2018, 02:11
  #32 (permalink)  
Join Date: Aug 2005
Location: UK
Posts: 32
CFM Shadow

During my short time as a Microlight Inspector I was asked to do the annual on a Shadow microlight.
Airframe checked, now for the engine. A pusher 2 stroke with a multi bladed prop.
I cracked up laughing and had to walk away, thinking this is a send up!
Was it a test on me? Very tempted to ask the owner to taxy it for but he might overheat the motor. Yep, all the blades on backwards! He assured me it flew alright!
Had a look round his hangar, no clue so asked to see the actual prop he had been using. Then he produced the unapproved one he had been using with all the moans about the approved prop being poor etc.
Oh dear.
straightfeed is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.