Rotary Wing Forum  

Go Back   Rotary Wing Forum > Kit Makers & Manufacturers > Air Command

Reply
 
Thread Tools Rate Thread Display Modes
  #1  
Old 08-17-2016, 05:25 AM
perbgyro's Avatar
perbgyro perbgyro is offline
Sport Pilot
 
Join Date: Dec 2007
Location: Austin, Texas
Posts: 350
Exclamation Air Command Cyclic POTENTIAL ISSUE!!

Shortly after takeoff from the PRA 65 meeting in Luling, I noticed the cyclic stick move abruptly to the left.
An immediate thought came to mind that it was NOT NORMAL and I didn't know if the cyclic control would be further compromised!
After a not so pleasant landing getting to the ground while I still had control, we noticed too much play in the cyclic pushrod connection fork.

IF YOU HAVE THE PUSHROD CONNECTION FORK CONSTRUCTION PICTURED HERE, I SUGGEST YOU INSPECT THE ASSEMBLY!
Attached Thumbnails
Click image for larger version

Name:	AirCmdCyclic1.JPG
Views:	220
Size:	145.6 KB
ID:	124655  
__________________
Paul Erb, Sport Pilot Gyro, PRA Chapter 65 Presidente www.centexpra.org
Reply With Quote
  #2  
Old 08-17-2016, 05:36 AM
perbgyro's Avatar
perbgyro perbgyro is offline
Sport Pilot
 
Join Date: Dec 2007
Location: Austin, Texas
Posts: 350
Default The issue!!

1) The Air Command pushrod connection fork is designed with one 1/8" thick 6061 Aluminum plate to hold the assembly together.
2) The bearings in the control tube attachment extends down and captures the bearings TO THE INSIDE!
3) The assembly allows play in the distance between the control tubes and the control tube/fork/bearing housing.

Once the plate bends and becomes distorted, the distance between the cyclic control tubes and the fork assembly allows the bearings to escape their housing and now the fork has further play because the assembly is riding on the bolt head and not the bearing.

If the control tube attachment plates that house the bearings comes free, ALL CYCLIC CONTROL CAN BE LOST!

My life depends on a single plate that can and does bend that allows the gap to open and come off the lower cyclic control tube.

This is a flawed design. The bearings should be on the outside for positive capture.
Attached Thumbnails
Click image for larger version

Name:	AirCmdCyclic (1).JPG
Views:	163
Size:	126.0 KB
ID:	124656   Click image for larger version

Name:	AirCmdCyclic.JPG
Views:	160
Size:	73.6 KB
ID:	124657  
__________________
Paul Erb, Sport Pilot Gyro, PRA Chapter 65 Presidente www.centexpra.org

Last edited by perbgyro; 08-17-2016 at 07:54 AM.
Reply With Quote
  #3  
Old 08-17-2016, 05:41 AM
perbgyro's Avatar
perbgyro perbgyro is offline
Sport Pilot
 
Join Date: Dec 2007
Location: Austin, Texas
Posts: 350
Default The fix

1) Remove as much flex from the system: Add a lower plate to sandwich the fork tubes.
2) Fork to control tube tolerance should be 3/4" plus the width of two washers
3) Add safety washers that would not contact the fork to control tube plates, but if there was an issue, the washers would force the assembly to retain the bearings and cyclic control. (that is how I flew the gyro back to the hanger)
4) New preflight items:
---a) look for proper clearance between washers and fork plates through all positions of the cyclic
---b) look for any signs that the washers have made contact with the fork plate surface.

I will post pictures of the corrected assembly once complete.
__________________
Paul Erb, Sport Pilot Gyro, PRA Chapter 65 Presidente www.centexpra.org

Last edited by perbgyro; 08-17-2016 at 05:48 AM.
Reply With Quote
  #4  
Old 08-17-2016, 06:32 AM
AirCommandPilot's Avatar
AirCommandPilot AirCommandPilot is offline
Just a fledgeling
 
Join Date: Feb 2014
Location: Houston
Posts: 267
Default

Quote:
Originally Posted by perbgyro View Post
1) Remove as much flex from the system: Add a lower plate to sandwich the fork tubes.
2) Fork to control tube tolerance should be 3/4" plus the width of two washers
3) Add safety washers that would not contact the fork to control tube plates, but if there was an issue, the washers would force the assembly to retain the bearings and cyclic control. (that is how I flew the gyro back to the hanger)
4) New preflight items:
---a) look for proper clearance between washers and fork plates through all positions of the cyclic
---b) look for any signs that the washers have made contact with the fork plate surface.

I will post pictures of the corrected assembly once complete.
I've noticed mine getting a tad bit of slop. I've been keeping an eye on it and check it before each flight. I guess this will be on the top of my list now. What was the purpose of them countersinking the holes like that. Was it to fit the bearing? I'm thinking a redesign is in my future.
__________________
Bobby Munroe
Private Pilot (SEL)
PRA Chapter 62 #42748
EAA #1160523
Reply With Quote
  #5  
Old 08-17-2016, 07:57 AM
perbgyro's Avatar
perbgyro perbgyro is offline
Sport Pilot
 
Join Date: Dec 2007
Location: Austin, Texas
Posts: 350
Default

Quote:
Originally Posted by AirCommandPilot View Post
I've noticed mine getting a tad bit of slop. I've been keeping an eye on it and check it before each flight. I guess this will be on the top of my list now. What was the purpose of them countersinking the holes like that. Was it to fit the bearing? I'm thinking a redesign is in my future.
I don't know the purpose, but the bearings should be captured on the outside of the fork to control tube plates. I would still reinforce with a second top plate to eliminate any thoughts of flexing.

I've had this gyro since 2007. Things look normal until there is a problem and then you look closely discovering the flaws.
__________________
Paul Erb, Sport Pilot Gyro, PRA Chapter 65 Presidente www.centexpra.org
Reply With Quote
  #6  
Old 08-17-2016, 08:07 AM
GyroCFI's Avatar
GyroCFI GyroCFI is offline
Gold Member
 
Join Date: Jun 2008
Location: Petersburg, Illinois
Posts: 803
Default

Quote:
Originally Posted by perbgyro View Post
1) The Air Command pushrod connection fork is designed with one 1/8" thick 6061 Aluminum plate to hold the assembly together.
2) The bearings in the control tube attachment extends down and captures the bearings TO THE INSIDE!
3) The assembly allows play in the distance between the control tubes and the control tube/fork/bearing housing.
When I was training with the Air Command Tandem I used to replace those angle plates every season, they were pretty cheap back then. Eventually, I changed and went to either a deeper bearing or double rows or something like that, I can't quite remember. but I did put large washers on the outside on each side to "capture" the assembly in case a bearing failed then the system would still operate albeit not at 100% but enough to get you down safely.
__________________
Don Randle
Gyroplane CFI

"Flying a Gyro is the most fun you can have with your clothes on!"
Reply With Quote
  #7  
Old 08-17-2016, 08:20 AM
RotorRambler RotorRambler is offline
Senior Member
 
Join Date: Nov 2009
Location: Plano, Texas
Posts: 277
Default

I know yours is a single-place Air Command, Paul, but I thought I'd add to this thread a link to the emergency bulletin at the Air Command website for a cyclic issue with its two-place models.

http://aircommand.com/safety1.php

Ira
Reply With Quote
  #8  
Old 08-17-2016, 11:21 AM
perbgyro's Avatar
perbgyro perbgyro is offline
Sport Pilot
 
Join Date: Dec 2007
Location: Austin, Texas
Posts: 350
Default

Quote:
Originally Posted by RotorRambler View Post
I know yours is a single-place Air Command, Paul, but I thought I'd add to this thread a link to the emergency bulletin at the Air Command website for a cyclic issue with its two-place models.

http://aircommand.com/safety1.php

Ira
Ira, thanks for that. I replaced my cyclic stick shortly after getting the machine because the aluminum stick was bending right at the cyclic control socket!
__________________
Paul Erb, Sport Pilot Gyro, PRA Chapter 65 Presidente www.centexpra.org
Reply With Quote
  #9  
Old 08-17-2016, 03:59 PM
shootthrees's Avatar
shootthrees shootthrees is offline
Tom Duncan
 
Join Date: Apr 2010
Location: Peachtree City, Georgia
Posts: 318
Send a message via Yahoo to shootthrees
Default

I replaced mine last year as well with 1/8th wall tube on my single. I felt that the previous builder had used tubing that was too thin.

Sent from my SAMSUNG-SM-G900A using Tapatalk
__________________
Kind Regards,

Tom Duncan

Blog: http://texassportpilot.blogspot.com/

PRA #42071
EAA #738671
AOPA #05028938

Member: Peach State Rotorcraft Club http://peachstaterotorcraft.org

“Success is peace of mind which is a direct result of self-satisfaction in knowing you made the effort to become the best of which you are capable.” - John Wooden
Reply With Quote
  #10  
Old 10-13-2016, 07:15 PM
perbgyro's Avatar
perbgyro perbgyro is offline
Sport Pilot
 
Join Date: Dec 2007
Location: Austin, Texas
Posts: 350
Exclamation Definitely an issue!

The fix is in!
I finally got around to adding the plate. The top plate was definitely deformed allowing the plates to spread and the bolts to slip out!
There is no movement now and tolerances are held bottom to top.
The hole is just from a cheek plate that the part was cut from.

the bottom bolt will have SS washers larger than the bolt and nut head to make sure nothing happens in flight again!

If you have this assembly with a single plate, I HIGHLY recommend adding the bottom plate to eliminate movement!

Now back to flying with confidence!
Attached Thumbnails
Click image for larger version

Name:	DediProg.JPG
Views:	90
Size:	143.7 KB
ID:	125469   Click image for larger version

Name:	DediProg (1).JPG
Views:	89
Size:	146.1 KB
ID:	125470   Click image for larger version

Name:	AC.jpg
Views:	96
Size:	30.5 KB
ID:	125471  
__________________
Paul Erb, Sport Pilot Gyro, PRA Chapter 65 Presidente www.centexpra.org
Reply With Quote
  #11  
Old 12-14-2016, 12:32 AM
jm-urbani's Avatar
jm-urbani jm-urbani is offline
Senior Member
 
Join Date: Dec 2010
Location: French Riviera
Posts: 124
Default

they have apparently learnt the lesson and modified their design ..; there are two plates now on above and one below just as you did

http://www.aircommand.com/tandemjoystick-detail.php
Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

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

Forum Jump


All times are GMT -8. The time now is 06:54 AM.


Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Ad Management plugin by RedTyger