Unusual Accident

[megan]

Wonder if a better preflight may have saved the day.Left rudder continuity was established from the cockpit rudder pedals to the rudder control horn; however, right rudder continuity could only be established from the cockpit rudder pedals to the cable end loop, which was not attached to the clevis at the rudder control hornhttps://s30121.pcdn.co/wp-content/uploads/2024/04/Report_ERA23FA045_106223_4_14_2024-12_58_27-AM.pdf

[OldLurker]

Wonder if a better preflight may have saved the day.Perhaps. The report states that the aircraft had previously done three sectors that day apparently without incident, two of them flown by the accident pilot (21,000-hour ATPL holder, apparently retired) and one by a friend, neither whom spotted the problem at preflight despite being aware of a “rigging issue”, and neither of whom seems to have felt that the “odd yawing” was serious. Moreover, the NTSB determined the probable cause of the accident to be “the pilot’s decision to unlatch his seatbelt during flight, which allowed him to exit the airplane and impact the tail, resulting in a loss of control and impact with terrain”, not the mis-rigging.

[Andrewgr2]

Perhaps. The report states that the aircraft had previously done three sectors that day apparently without incident, two of them flown by the accident pilot (21,000-hour ATPL holder, apparently retired) and one by a friend, neither whom spotted the problem at preflight despite being aware of a “rigging issue”, and neither of whom seems to have felt that the “odd yawing” was serious. Moreover, the NTSB determined the probable cause of the accident to be “the pilot’s decision to unlatch his seatbelt during flight, which allowed him to exit the airplane and impact the tail, resulting in a loss of control and impact with terrain”, not the mis-rigging.

But it seems very likely that the pilot only undid his harness to look at the rudder to see why the aircraft had strange yaw characteristics. The disconnected rudder cable should have been easy to spot in a pre-flight inspection- and should certainly not have escaped whatever inspection was done after work had been done on the rudder.

[Hot 'n' High]

But it seems very likely that the pilot only undid his harness to look at the rudder to see why the aircraft had strange yaw characteristics. The disconnected rudder cable should have been easy to spot in a pre-flight inspection- and should certainly not have escaped whatever inspection was done after work had been done on the rudder.

I agree the first part of your comment. However, the report mentions that the right clevis pin made it to the accident site so, quite possibly, the cable was connected to the rudder until impact. The problem could have been something like a broken pulley bracket or tensioning spring somewhere in between which may only have manifested itself if a "positive control check" had been carried out (as per a glider after rigging where someone holds the control surface still while another tries to waggle the appropriate cockpit control). Even that may have required further more detailed engineering inspection as it would probably not have been clear where in the run the issue was.

I guess the "take-home" is, if a plane is telling you something is not quite right, do an appropriate set of engineering checks on the ground before committing aviation in it! All in all, a very sad accident........ :uhoh:

[42go]

Last time I flew a Cub I would have had to do more than undo my straps to 'fall out' and hit the tailplane?? Was he making his way back along the outside of the fuselage to check the rudder? :confused:

[EXDAC]

If the rudder was disconnected before the flight how does anyone explain that the clevis pin was found at the accident site? Rudder horn clevis pins are typically retained by a cotter pin (split pin UK). If the cotter pin was missing the crash could possibly have caused the clevis pin to fall out. The clevis pin should always be installed head up so it is not likely to fall out in positive g flight.

If a clevis pin was missing on my tailwheel aircraft it would be obvious when I pulled the aircraft out of the hangar, obvious at first attempt to taxi, and if I somehow got that far, would likely cause loss of control at start of takeoff roll.

Sorry, but there is no way this rudder was disconnected when the aircraft took off. It is also unlikely that a missing split pin contributed in any way to the flight anomaly that was being investigated.

[EXDAC]

I have personal experience that an improperly adjusted tailwheel swivel bearing will cause similar results to the issue this owner was investigating. If the swivel king pin nut is too tight the tailwheel will resist the steering spring as the rudder is deflected. Add a little more rudder pedal force and the tailwheel breaks out causing a sudden rudder movement. It is a very unpleasant control response and one that I knew had to be fixed on the ground before further flight.

In my case the improper adjustment was made in an attempt to eliminate tailwheel shimmy.

[biscuit74]

Last time I flew a Cub I would have had to do more than undo my straps to 'fall out' and hit the tailplane?? Was he making his way back along the outside of the fuselage to check the rudder? :confused:

I wondered that too. It may be, since he was a retired man, he was somewaht stiff and found it hard to turn around ? I have one friend like that, who has great difficulty climbing into his aircraft but is fine once aboard. Undoing all the harness while airborme seems counter-intuitaive to me; I'd have perhaps slipped off the shoulder straps, which would still let me turn around enough to see the tail. As an ex-airline pilot, he will have been much more used to the idea of flying whilst not strapped in, and to tthe idea of moving around in the aircraft while flying. Maybe his background lulled him. Horrible accident - and yes the possibility of a tailwheel steering hang up causing this sort of effect sounds very plausible,

[EXDAC]

I have personal experience that an improperly adjusted tailwheel swivel bearing will cause similar results to the issue this owner was investigating.

The accident docket photos show the tailwheel was not a Scott 3200 or an ABI 3200 clone of the Scott. The Bearhawk uses an in-house tailwheel design and I do not know if it can be adjusted incorrectly like the Scott and clones.

https://bhtailwheels.com/our-tailwheels

[Maoraigh1]

Some tailwheels have a plate with a hole into which a ball clicks. If the plate cracks, taxiing is a continuous correction of turning left/right. I've taxied a Jodel DR10 for almost a mile on tarmac with this condition. Surprisingly the replacement plate was cheap and in stock in the UK, so this must be quite common.