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CH701 Door Warning

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vgstol(at)bigpond.net.au
Guest

Posted: Tue Apr 01, 2008 6:23 pm Post subject: CH701 Door Warning

 

[b]Reporting on an incident that could have had serious  consequences...<?xml:namespace prefix = o ns =  "urn:schemas-microsoft-com:office:office"  /> 

  

The CH701 was flying straight and level at 70 kts on a  cross-country flight. 

While reaching for a water bottle, the pilot accidentally  snagged the left-hand inner door handle, releasing the door.  The door instantly slammed up against  the bottom of the wing, with such impact that the outer handle punched a hole  through the wing skin.  The pilot  grabbed and held the door with one hand, and slowed the aircraft.  But the front hinge had broken with the  initial impact, causing the door to skew somewhat across the wind.  The resulting force was so strong that  the pilot couldn’t pull the door in again, even at 50kts.  Eventually he had to let it go.  When it went, it hit the horizontal  stabilizer, causing considerable damage to the leading edge, breaking the left  forward mounting bracket (7.H.2.6), and bending the right forward bracket.  So the horiz stab was then somewhat skew  to the fuselage. 

  

The aircraft was still flyable, but with considerable  drag and a left yaw bias.  The pilot  continued on to an airfield and made a successful landing.   

  

For photographs and analysis have a look at   

 http://www.stolspeed.com/701-door-warning/   

  

JG[/b]

n801bh(at)netzero.com
Guest

Posted: Tue Apr 01, 2008 8:30 pm Post subject: CH701 Door Warning

And this warning comes from the guy who swears by VG's. Funny this 701 was cruising at only 70 knots..... 

do not archive



  

[b]Reporting on an incident that could have had serious consequences...<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> 

  

The CH701 was flying straight and level at 70 kts on a cross-country flight. 

While reaching for a water bottle, the pilot accidentally snagged the left-hand inner door handle, releasing the door.  The door instantly slammed up against the bottom of the wing, with such impact that the outer handle punched a hole through the wing skin.  The pilot grabbed and held the door with one hand, and slowed the aircraft.  But the front hinge had broken with the initial impact, causing the door to skew somewhat across the wind.  The resulting force was so strong that the pilot couldn’t pull the door in again, even at 50kts.  Eventually he had to let it go.  When it went, it hit the horizontal stabilizer, causing considerable damage to the leading edge, breaking the left forward mounting bracket (7.H.2.6), and bending the right forward bracket.  So the horiz stab was then somewhat skew to the fuselage. 

  

The aircraft was still flyable, but with considerable drag and a left yaw bias.  The pilot continued on to an airfield and made a successful landing.  

  

For photographs and analysis have a look at  

 http://www.stolspeed.com/701-door-warning/  

  

JG[/b]

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   [quote][b]

vgstol(at)bigpond.net.au
Guest

Posted: Wed Apr 02, 2008 12:35 am Post subject: CH701 Door Warning

There's now a follow-up on  the door incident page at 

 [url=]http://www.stolspeed.com/701-door-warning/[/url]  

 JG

 [quote]   ---

zodierocket(at)hsfx.ca
Guest

Posted: Wed Apr 02, 2008 3:23 am Post subject: CH701 Door Warning

Part I don’t understand is that I have opened the doors in flight several times and they have never flown up, they hover about 4 inches away from closed. Must be that laminar flow from the VG’s that ahs sucked all the air to the top of the wing. OK bad joke , but honestly I have never deemed them as a worry.  

     

Mark Townsend  Alma, Ontario  

Zodiac 601XL C-GOXL, CH701   

www.ch601.org / www.ch701.com/ www.Osprey2.com  

  

--

kmccune

Joined: 22 Sep 2007
Posts: 577
Location: Wisconsin, USA

Posted: Wed Apr 02, 2008 7:33 am Post subject: Re: CH701 Door Warning

Yup, and getting very good fuel economy while doing it!

Do not archive

[quote="n801bh(at)netzero.com"]And this warning comes from the guy who swears by VG's. Funny this 701 was cruising at only 70 knots..... 

do not archive



  

[b]Reporting on an incident that could have had serious consequences...<xml> 

  

The CH701 was flying straight and level at 70 kts on a cross-country flight. 

While reaching for a water bottle, the pilot accidentally snagged the left-hand inner door handle, releasing the door.  The door instantly slammed up against the bottom of the wing, with such impact that the outer handle punched a hole through the wing skin.ï¿½ The pilot grabbed and held the door with one hand, and slowed the aircraft.  But the front hinge had broken with the initial impact, causing the door to skew somewhat across the wind.  The resulting force was so strong that the pilot couldnï¿½t pull the door in again, even at 50kts.  Eventually he had to let it go.  When it went, it hit the horizontal stabilizer, causing considerable damage to the leading edge, breaking the left forward mounting bracket (7.H.2.6), and bending the right forward bracket.  So the horiz stab was then somewhat skew to the fuselage. 

  

The aircraft was still flyable, but with considerable drag and a left yaw bias.  The pilot continued on to an airfield and made a successful landing.  

  

For photographs and analysis have a look at  

 http://www.stolspeed.com/701-door-warning/  

  

JG[/b]

 	  Quote: 	
		  



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">http://www.matronics.com/Navigator?Zenith-List

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Proven Hair Replacement Options. Click here.

   [quote][b][/quot

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Dorothy McCune

ruruny(at)aol.com
Guest

Posted: Wed Apr 02, 2008 10:20 am Post subject: CH701 Door Warning

Actually I have had a concern about this since my demo ride at the factory years ago.

 We never opened the doors in flight, but while taxiing out we left them unlatched. 

 When Roger pushed in the throttle more the doors opened more. My door is attached with a 

 piano hinge the length of the top of the door, not a front or rear hinge.

 I've always figured they would fly open as has happened in this incident. I thought about a safety pin

 installed on the plate attached to the fuselage. Close latch, insert pin behind latch into plate.

 Or just a blind A5 rivet in that same hole where the pin would go to make a detent.  

 How can a door on one plane fly up and another it not. The shape of the door is curved outward at the base of the

 window, creating an airfoil which would cause it to fly open.

 It would be a cool test in a wind tunnel. Thanks for the report on this.

 

 Brian Unruh

 http://www.701builder.com Get the MapQuest Toolbar, Maps, Traffic, Directions & More! 

  [quote][b]

vgstol(at)bigpond.net.au
Guest

Posted: Wed Apr 02, 2008 6:45 pm Post subject: CH701 Door Warning

I’m more than a bit concerned  about the flippant and dismissive initial comments that could tend to deflect  the attention of other aircraft owners and builders from a potential situation  they should consider seriously.  

  

None of us have deemed these  doors a worry, but this incident shows the potential otherwise!  It was a very close call to a  real disaster, and not due to any fault in the aircraft involved or actions of  the pilot – it could happen to any of us with similar construction doors.   

  

At this point I must emphasize that I am  very careful in all my work to not make any claims that aren’t backed by  experience and preferably repeatable testing.  If I state an opinion that’s just based  on speculation or theory or hearsay, I always try to preface the statement to  clarify that basis.  

  

Many of us would have tried  flying the door partially open, and found them to seem stable in the  airstream.  Further examination of  the remains of the door, and speculation as to how such violent forces could  develop that would rip the door in two, are very sobering because it  demonstrates that the potential is always there for everyone. 

  

Some understanding of  aerodynamics, some understanding of structures, and common sense analysis leads  me to the following speculations: 

  

A practical demonstration  would be to remember what it’s like to hold your hand outside the car window at  road speed.  Keeping it flat and  parallel to the airstream it just floats, but increase the angle of attack just  a little bit and it zooms up.  Now  imagine trying that experiment while holding a small flat plate at a speed of  80mph!  The aerodynamics of a flat  plate are such that at zero AoA the lift is zero, but a small increase in AoA  generates an enormous lift instantly.   Now extend that vision to a flat plat of the area of the door at 80mph  and the lift would be enormous.    

  

Now imagine taking a hammer  and hitting the bottom of your wing as hard as you can – probably get a big ugly  dent.  The impact from this incident  drove the outside door handle right through the wing skin!  The door itself has very little mass, so  the velocity must have been extremely high to generate enough momentum to cause  that puncture! 

  

The photo in the website below  shows the remains of the door.  It  turns out that the front hinge didn’t break – the door frame broke at the front  of the front hinge, and below the gas strut attach point on the rear, and tore  the 2mm thick polycarb diagonally across.    

  

I think that break just below  the strut attach point is a key clue.   The function of the gas strut is like a shock absorber, considerably  slowing the movement of the door both up and down.  These lightweight doors are very  flexible, particularly in torsion.   If a swirl of the slipstream got under the leading edge, forcing it up  suddenly, the damping effect of the strut would cause the door to flex and  increase the angle of attack considerably, thus increasing the lift force  enormously.  This is now an unstable  situation where increasing flex of the door leads to increasing lift force which  leads to increasing flex which leads to even more lift force........  This scenario would account for the  evidence as I see it. 

  

Going from a stable situation  of the door just floating there, to a dramatic and violent episode can happen  instantly, and without any warning!   Please keep this scenario in mind whenever you consider having a door  open to the slipstream!!  It’s not a  fault in the design of the 701 door, it’s just a fact of life, and also  applicable to any other doors of similar design. 

  

This morning I received  feedback from someone who built a 701 about 7 years ago, and says that he  remembers hearing of a very similar incident about that time, where the door  ripped off and damaged the horiz stab, resulting in a crash landing that very  much damaged the aircraft......     

Does anyone else remember that  incident?? 

  

 There are now more photographs, and  analysis of possible fixes and preventative measures at  

http://www.stolspeed.com/701-door-warning/  

 [quote]   ---

graeme(at)coletoolcentre.
Guest

Posted: Wed Apr 02, 2008 8:34 pm Post subject: CH701 Door Warning

Thanks for the warning I for one took it in the  manner it needed to be taken.

 I could see the situation happening and am now  aware of another thing to watch for.

  

 Both my catches are quite firm but will make sure  my passengers are aware don't touch door lock in flight.

 Graeme Cns

 [quote]   ---

david_a_g_johnson(at)btin
Guest

Posted: Thu Apr 03, 2008 1:07 am Post subject: CH701 Door Warning

It seems to me that this could be more of a problem  with the optional bulged doors, which must form a pretty good airfoil trying to  pull the door open.

  

 Dave Johnson

  

 601XL (so I don't really know what I'm talking  about!)

  

 do not archive

  

 [quote]   ---

Tommy Walker

Joined: 12 Jan 2006
Posts: 442
Location: Anniston, AL 36207

Posted: Thu Apr 03, 2008 1:59 pm Post subject: Re: CH701 Door Warning

Brian,



I've thought about this too.  



And I appreciate Mr. JG bringing it to our attention.



Folks, as far as I know, Mr. JG is NOT trying to sell us a "fix" for this problem.  I am looking at ways to lessen the potential for an in-flight door departure.



Tommy Walker in Alabama

N8701 44.8 Hours

Phase I Finished!



[quote="ruruny(at)aol.com"]Actually I have had a concern about this since my demo ride at the factory years ago.

 We never opened the doors in flight, but while taxiing out we left them unlatched. 

 When Roger pushed in the throttle more the doors opened more. My door is attached with a 

 piano hinge the length of the top of the door, not a front or rear hinge.

 I've always figured they would fly open as has happened in this incident. I thought about a safety pin

 installed on the plate attached to the fuselage. Close latch, insert pin behind latch into plate.

 Or just a blind A5 rivet in that same hole where the pin would go to make a detent.  

 How can a door on one plane fly up and another it not. The shape of the door is curved outward at the base of the

 window, creating an airfoil which would cause it to fly open.

 It would be a cool test in a wind tunnel. Thanks for the report on this.

 

 Brian Unruh

 http://www.701builder.com Get the MapQuest Toolbar, Maps, Traffic, Directions & More!

_________________
Tommy Walker
N25A - Anniston, AL

cgbrt(at)mondenet.com
Guest

Posted: Sun Apr 06, 2008 4:06 am Post subject: CH701 Door Warning

---

ricklach

Joined: 20 Jun 2006
Posts: 127
Location: Kernville, Calif.

Posted: Sun Apr 06, 2008 7:31 am Post subject: Re: CH701 Door Warning

Hi John (JG),



I would like to thank you for your continuing effort to innovate changes in a proven design for the thrill and safety of flying, and then sharing the results with us. Iâ€™ve always thought the door assembly was a little light but never thought about the possible results of a mishap like Hans went through. I like your new latch solution. Could you please post some more photos on your web sight.



Itâ€™s always interesting to read your post.



Rick

vgstol(at)bigpond.net.au
Guest

Posted: Sun Apr 06, 2008 12:12 pm Post subject: CH701 Door Warning

Gday  Carl,

  

 No this was the old style  door.  An early model.  

 They were very  flexible.  In the re-build Hans used .060 instead of .025 for the corner  gussets, and that made a much stiffer and better feeling  door.

  

 Basically I think any door  has this potential if the airflow catches it just wrong, then everything  will change instantly.

  

 Tailwinds  always,

 JG

  

 ---

vgstol(at)bigpond.net.au
Guest

Posted: Sun Apr 06, 2008 12:53 pm Post subject: CH701 Door Warning

Thanks  for your supportive comments Rick.

  

 Those  heavier gussets in the corners really made a big difference in the stiffness of  the door.  That was an early model door, and they are a little bit  different from the later model in Hans own aircraft.  In the early model  there was a gusseted corner at the bottom of the trailing edge, whereas the  later model has the tubing sweeping around a radius corner in one  piece.  That gusseted corner is the source of much of that  flexibility.

  

 The  main part of that latch is pretty standard, but the sliding rod to the trailing  edge is a new idea borrowed from a Rans S7.  We still have to get  it to work on the aircraft, which is a 6 hour drive away.  I'll post more  photos when it's fully installed.

  

 Tailwinds  always,

 JG

 [quote]   ---

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