Go Back  PPRuNe Forums > Aircrew Forums > Rotorheads
Reload this Page >

Chinooks, further upgrade for forward flight in gyroplane mode

Rotorheads A haven for helicopter professionals to discuss the things that affect them

Chinooks, further upgrade for forward flight in gyroplane mode

Old 28th Jan 2018, 08:11
  #1 (permalink)  
Thread Starter
 
Join Date: Jun 2014
Location: Singapore
Posts: 17
Chinooks, further upgrade for forward flight in gyroplane mode

I am not an engineer but may I discuss a question.

It is possible to configure the engines of Chinooks to provide forward thrust for forward flight, such that the rotors can be unloaded and even fly as gyroplane in forward flight.

Even if you may need to upsize the engine, would this be a easier (cheaper, safe in terms of less technological risks) way of getting more speed, rather than to having to put additional pusher propellers like in the case of X2?

Thank you.
horlick97 is offline  
Old 28th Jan 2018, 09:15
  #2 (permalink)  
 
Join Date: Sep 2002
Location: Great South East, tired and retired
Posts: 3,737
Helicopter engines are designed to extract the maximum energy from the fuel burnt and send it to the gearboxes, with little left over at the tailpipe, maybe 50lb thrust.

Turbojet engines take as little as possible from the fuel burnt to leave it with more energy blasting out the back, i.e. thrust. Completely different designs.

And for a Chook to turn into a gyrocopter, the blades have to go from sucking air in at the top and pushing it down to generate lift and thrust (and being tilted forward), to then go to being tilted back and having air come in from underneath, and extract energy from it to stay up (autorotation mode). Again, a big jump to make.

With pusher props from another engine, and with stubby wings to provide lift, the rotors can be unloaded (not turned into gyrocopters), which just means it can fly with less collective lever, using less fuel.
Ascend Charlie is online now  
Old 28th Jan 2018, 09:23
  #3 (permalink)  
 
Join Date: Feb 2005
Location: Zummerset
Posts: 1,013
The Boeing 347 was a lift compounded version of the Chinook to unload the rotor system. It was abandoned after flight tests as not providing a big enough advantage to warrant the development costs as the US Army at the time was perfectly happy with what they had. Nowadays, with advances in digital engine and rotor control, and more advanced modelling of aerodynamics, it would likely be a smoother and easier process. However, there would still need to be a requirement to do so - and a "clean sheet" design may well be more efficient.....
Evalu8ter is offline  
Old 28th Jan 2018, 11:50
  #4 (permalink)  
 
Join Date: Mar 2016
Location: Underneath the Radar
Posts: 160
rrekn is online now  
Old 28th Jan 2018, 17:06
  #5 (permalink)  
 
Join Date: Jul 2011
Location: Secret hide-out in the Rocky Mtns
Age: 71
Posts: 22
Originally Posted by horlick97 View Post
would this be a easier (cheaper, safe in terms of less technological risks) way of getting more speed
There's still the issue of retreating blade stall which limits Vne, so what would be the point?
Helicodger Pilot is offline  
Old 28th Jan 2018, 20:09
  #6 (permalink)  
 
Join Date: Sep 2002
Location: Great South East, tired and retired
Posts: 3,737
If there is a wing providing lift, then the retreating blade doesn't have to work so hard, and the stall will occur at a higher speed.

And Vne is less dependent on RBS than other factors.
Ascend Charlie is online now  
Old 28th Jan 2018, 20:55
  #7 (permalink)  
 
Join Date: Nov 2015
Location: Farnham, Surrey
Posts: 1,308
The "compound helicopter" operates on the principle that in the cruise the wing generates the lift to carry the weight while the rotor is run at zero (collective) pitch and is just used for pitch/roll control (cyclic). At zero pitch there is no retreating-blade stall. But this is only true for a proper compound helicopter where there is both a fixed wing AND a separate means of forward propulsion.

PDR
PDR1 is offline  
Old 28th Jan 2018, 22:14
  #8 (permalink)  
 
Join Date: May 2017
Location: The Great Sovereign State of Texas
Posts: 18
Being an old, stubborn-ass, died in the wool, West Texas boy who cut his teeth on the stuff coming out of Ft. Worth (Hurst) way back in the day..., I'd be doing myself a huge injustice if I didn't mention the Bell 533. Late 1950's through late 1960's technology.

(...being that I still don't have my secret clearance to post pictures, y'all just gonna have to "cut and paste")



4.bp.********.com/-2vTNUzqr48c/T1nwZdarL0I/AAAAAAABVWY/gtTTxozj7H8/s1600/Bell533-bia2.jpg




Last edited by Senior Pilot; 29th Jan 2018 at 04:47. Reason: Fix image links: blog spot will not work on PPRuNe
SandBlaster214 is offline  
Old 29th Jan 2018, 00:14
  #9 (permalink)  
 
Join Date: Oct 2002
Location: 1 Dunghill Mansions, Putney
Posts: 1,797
Originally Posted by Ascend Charlie View Post
If there is a wing providing lift, then the retreating blade doesn't have to work so hard, and the stall will occur at a higher speed.
...Which was the driver behind the Unload Lift Offset Rotor (ULOR) concept.



I/C
Ian Corrigible is offline  
Old 29th Jan 2018, 03:46
  #10 (permalink)  
 
Join Date: Sep 2002
Location: Great South East, tired and retired
Posts: 3,737
Oh, that is sooooo ugly. Did it ever get beyond a concept? Those engines look like they were borrowed from a Hercules.
Ascend Charlie is online now  
Old 29th Jan 2018, 09:26
  #11 (permalink)  
 
Join Date: Nov 2015
Location: Farnham, Surrey
Posts: 1,308
Well the examples I would have chosen would have been the Lockheed experimental XH-51A:



And the AH-56 Cheyenne attack helicopter developed as a result:



The AH-56 Cheyenne programme developed and matured most of the features seen on subsequent attack helis - integrated nav/attack, helmet-slaved gunsighting etc.

PDR
PDR1 is offline  
Old 29th Jan 2018, 10:39
  #12 (permalink)  
 
Join Date: Apr 1998
Location: Mesopotamos
Posts: 1
I suspect if/when the all electric tail rotor becomes a reality then it would be quite a simple task to make it pivot around from providing anti-torque at low speed to providing forward propulsion at high speed.
cattletruck is offline  
Old 29th Jan 2018, 11:20
  #13 (permalink)  
Thread Starter
 
Join Date: Jun 2014
Location: Singapore
Posts: 17
Originally Posted by cattletruck View Post
I suspect if/when the all electric tail rotor becomes a reality then it would be quite a simple task to make it pivot around from providing anti-torque at low speed to providing forward propulsion at high speed.
Thanks everyone for all the comments and input.

Regarding this above concept ("to make it pivot around from providing anti-torque at low speed to providing forward propulsion at high speed"), I have also been thinking about similar concept.

But, there will still be the problem of RBS, unless there is a set of fixed wing, right?
horlick97 is offline  
Old 29th Jan 2018, 12:37
  #14 (permalink)  
 
Join Date: Oct 2002
Location: 1 Dunghill Mansions, Putney
Posts: 1,797
Originally Posted by Ascend Charlie View Post
Oh, that is sooooo ugly. Did it ever get beyond a concept?
Charlie,

I don't believe so. The last time I saw ULOR referenced was at the AUSA annual convention in October 2011, 3 years after the concept first appeared at AHS Forum 64 (and 4 years after the idea was patented).

Those engines look like they were borrowed from a Hercules.
One development that does appear to be proceeding is installation of the CH-53K's 7,500 shp GE T408 engine on the CH-47F, in place of the current 4,867 shp T55-L-714A. The T408 - whose heritage includes the T407 prop unsuccessfully offered for the C-130J in the early 1990s - will nearly quadruple the Chinook's installed power from the 1,940 shp YT55-L-5 installed in the original YHC-1B.

I/C
Ian Corrigible is offline  
Old 29th Jan 2018, 13:29
  #15 (permalink)  

Avoid imitations
 
Join Date: Nov 2000
Location: Wandering the FIR and cyberspace often at highly unsociable times
Posts: 13,682
Originally Posted by horlick97 View Post
Thanks everyone for all the comments and input.

Regarding this above concept ("to make it pivot around from providing anti-torque at low speed to providing forward propulsion at high speed"), I have also been thinking about similar concept.

But, there will still be the problem of RBS, unless there is a set of fixed wing, right?
You mean rather like this?

ShyTorque is offline  
Old 30th Jan 2018, 12:10
  #16 (permalink)  
 
Join Date: Oct 2009
Location: Old Hampshire
Age: 66
Posts: 607
[QUOTE
Regarding this above concept ("to make it pivot around from providing anti-torque at low speed to providing forward propulsion at high speed"), I have also been thinking about similar concept.
[/QUOTE]


I think you'll find someone already had that idea in the 1930's, its called the Gyrodyne.
VX275 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 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.