RV-7/7A In-Flight Breakup Accident Information

[RV8JD]

There was some interest in a previous thread regarding the status of the investigations into the RV-7/7A in-flight breakup accidents that have occurred.

I put together the attached spreadsheet documenting the accidents I am aware of. The spreadsheet has embedded links to the respective national safety board's investigation reports, links to the dockets where available, and links to some references.

I plan to update this spreadsheet as necessary. If there are any accidents I missed, please let me know.

Clicking on the image below will take you to the spreadsheet.



Fly safe!

[Taltruda]

What are you finding to be a common link? Is it the ripper rudder coming apart from possible over speeds?

[swift12]

"Aircraft pitch is approximately 30° nose-down, wings almost level. The
IAS is recorded at 244kts"

ZK DVS....it appears commonality among some accidents is overspeed. slippery aircraft flying close to VNE pointing downwards not a good mix. I flew a lancair many years ago and came to the conclusion it was awesome to roll and a lawn dart pointing downhill...its ok...but not if you screw it up. I went over VNE pulling out and eased off...luckily the surfaces did not flutter. Id like to see the rudder have a 50% margin on the speed before breakup...maybe 300 knots but perhaps thats unrealistic.

I do wonder if the "8" rudder is better in this respect being a folded trailing edge? seeing these rudders fold in the wind is a little worrying.

In this case rudder flutter caused the vertical stab to separate and one wonders if the surface was balanced well....

quote..."Van’s Aircraft has conducted stick raps and rudder pedal kicks testing to 220kts, 8 with no indication of flutter up to this airspeed. Flight at any airspeed over Vne, however, exposes the aircraft to the possibility of flutter"

I tend to think that there is somewhat of a variance in what might be experienced between different aircraft and balance of the flight controls should be of paramount importance especially after painting. You simply cannot take flutter with a grain of salt...it destroys aircraft.

So in that case..no doubt vans has done extensive testing and in the normal envelope with balanced controls we have nothing to worry about...but overspeed or overload and add flutter.....mmmm.....poor buggers.

Its a timely reminder to do two things...
1. balance your controls
2. don't fly outside the manoeuvring speeds or g loading. if you do...carefully recover....

[AndrewR]

I wonder how much difference builder to builder variations in the training edge make?

It would be interesting to compare differences in the stiffness of rudders on different aircraft. It might not require much shear movement in the trailing edge before balancing becomes ineffective because the top and bottom flutter independently.

A folded trailing edge seems like it would be much stiffer.

[plehrke]

Originally Posted by AndrewR

A folded trailing edge seems like it would be much stiffer.

Remember that folded rudders also tend to have a dab of RTV or proseal at the end of each stiffener to help prevent skin cracking. That will tie skin and stiffeners all together making a much more robust trailing edge.

[Snowflake]

I have the full report on C-GNDY from the TSB. In addition to the overspeed in flight (also over 240 kt if I recall) the conclusion was that the rudder was severely unbalanced. It had been inspected in an unpainted condition, and afterwards it was painted and that included some significant (up to 1/8" thick) filler used smooth the rudder and elevator surfaces. There was no evidence that the surfaces were re-balanced after the paint job.

So in addition to keeping speeds under Vne, keep your control surfaces balanced.