Service Bulletin SNX-SB-011 - throttle and mixture

[karmarepair]

Flyers in particular, have you seen Service Bulletin SNX-SB-011?
https://www.sonexaircraft.com/service-b ... s/#general

"Status Models and Serial Numbers. Date of Issue . Reference Number
REQUIRED All Legacy Sonex, Waiex and Xenos Airframes 05.31.22 SNX-SB-011
Unsafe Center-mounted Throttle Installations:
A common builder modification is to move the throttle (and mixture control) to the center of the cockpit, but leave the flap lever and brake lever on the left wall of the cockpit. This creates a dangerous need to change hands on the joystick during critical phases of flight (climb-out, maneuvering, landing, go-around). Moving ONLY the throttle (and mixture control) to the center of the cockpit is NOT a Sonex-approved control configuration.
The cockpit MUST be configured so one of the pilot’s hands can remain on the stick at all times while the other hand remains free to operate the other controls (throttle, mixture, flaps, brakes, trim).
Corrective Actions:
If a center-mounted throttle is necessary, the flap and brake handles (as well as mixture control and trim control) MUST be moved to the centerline of the aircraft. Sonex specifically designed the Sport Trainer (ST) modification to accommodate center-mounted controls.
- SNX-C08_OptionalCenterControls_A.pdf
- SNX-C09_OptionalCenterDetails_A.pdf
If a center-mounted throttle is not necessary, the throttle (as well as mixture control and trim control) MUST be moved to the left side of the cockpit, near the flap and brake handles."

Please discuss. Do you plan to comply?
Previous builders set my Soon-To-Be-Flying airplane up EXACTLY the way Sonex is saying it shouldn't be. I haven't installed the glare shield and windscreen yet, so changing the throttle and mixture IS do-able, but it's going to take time.

[GraemeSmith]

Bear with me......

In 1938 - the first 300 Supermarine Spitfires were laid out:

Throttle / Mixture / (and after conversion to adjustable pitch) Prop control - LEFT SIDE COCKPIT
Flap switch - air line - TOP LEFT PANEL
Stick - CENTER
Gear Pump - RIGHT SIDE COCKPIT

A consequence of this layout was that at take off the pilot advanced the throttle with their left hand while flying with the right. As the aircraft became airborne and was hanging on (in the early days) a slow turning fixed pitch prop.... To get the gear up - the pilot switched hands on the stick leaving the throttle unguarded - now flying with their left hand on the stick - they reached for the wobble pump handle with their right hand - unlocked the gear, and 60-100 pumps later (about a minute) the gear was up. During the pump up the pilot tended to introduce pilot induced pitch oscillations on the stick as they pumped away with their right hand. The throttle was depending on the throttle friction to hold it. Setting the throttle friction prior to take off was emphasized in the pilot notes. It was a dreadful arrangement with near stalls from the PIO's or from throttles slipping. And completely distracted the pilot during a critical phase of flight. The arrangement was quickly changed with a small hydraulic pump to get the gear up. The pilot still had to change hands on the stick for a moment - but it was infinitely better. Landing was a bit easier - you could get the gear down (pressure blew it down) while abeam the numbers and then right hand flew the plane while left hand worked throttle and prop and could reach up to flick the flap switch (flaps were all or nothing) on the panel.

--

Fast forward - try and find a CFI prepared to give transition training in a Sonex type with everything out of reach to the CFI on the left cockpit wall. They are like hen's teeth.

Try and improve things by moving SOME of the stuff to the center - but not all of it. Not much better. In fact WORSE - because you are now left with divided hand attention - per the factory's concerns.

--

I fly a lot of fighter style, curved approach landings and wherever possible the power is off from abeam the numbers till touch down. My right hand is on the stick and my left hand adjusts flaps as needed while making the approach. On a good day - that's all I need to do. But just sometimes if I am coming up slightly short - I'm going to need a touch of power. It is a momentary 12 inch change of left hand position to achieve this from flap handle to throttle while the right hand flies the plane. It requires absolutely PROMPT attention sometimes if it is slightly gusty. There is NO SAFE AMOUNT of time to switch hands to get to a center mounted throttle when my left hand was on the flaps a moment before. NONE. If I was at flaps 30 and need to go 20 for a go around as I apply full power - you can't do it or switch hands fast enough at a SUPERCRITICAL phase of flight.

IMO - Sonex are absolutely right to point out split control configurations as dangerous.

--

Rather amazingly I managed to find a CFI prepared to do my 10 hours transition training for insurance with my all left set up. But we expressly agreed that it was OK for him to completely invade my personal space - if he had to - reach across me to get at the throttle or trim. There was no good answer for the flaps - he would have no mechanical advantage with his body twisted to operate them. We proceeded with caution on long runways till he got happy that I could fly the plane and would respond to instant commands to adjust the flaps. :-)

[Bryan Cotton]

I agree with Sonex especially now at 28.5 hours. I built mine with sport trainer (center) controls so I can fly from either seat.

[builderflyer]

In my opinion you definitely want to comply with this service bulletin. If you should experience difficulty in retracting the flaps (as many of us did prior to modifying the full flap detent) and at the same time you experience the throttle creeping to idle (as many of us did prior to getting the throttle friction lock dialed in) both occuring on a go-around at low altitude, you'll find yourself in a really uncomfortable and dangerous situation. So make the change now and have one less regret later.

Art,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,Jabiru 3300 #261/Aeroinjector

[racaldwell]

I agree. You need to keep a hand on the stick and work everything else with the other hand.

I have a center throttle so I made a center mounted spoiler handle so I don't need the one on the left. It's still there as a back up but I have never used it since making the center actuator. I found out the hard way that to go around in a dicey gusty, crosswind situation that the having an important control lever out of reach for the throttle hand is a very bad idea when there is no time to be switching hands on the stick.

Rick Caldwell
Xenos 59 hrs.

[n502pd]

Yes, indeed, I wholeheartedly agree with what the service bullitin requires us to consider! When building Sirpeedee, sometime in 2014 or thereabouts, laying out the controls, in my feeble mind, did not want to take my hand off the stick, for anything. Therefore, I configured as sport trainer from the beginning, and consider ALL controls,flaps, brakes,trim,etc, in the center as a necessity to be safe. If a PAX needs to take control for unforseen pilot incapacity, then there is a good chance things may turn out ok. With controls split, or all on the left side only, very little chance exists for a happier ending.

I am very pleased with the sport trainer mod, and lowered seat mod, I did durring my build. I highly suggest all consider compliance, one way or the other,all left side, or all in center, but not split locations. Of course, Juse IMHO!

PS:Merry Christmas to all!!

[karmarepair]

Looking through Jeff Schultz's collection of panel photos, there are a surprising number of people who put the throttle and mixture in the middle WITHOUT the center flap actuator and trim, I.E. the configuration Sonex condemns.
http://www.sonex604.com/other_panels.html There are 4 pages.
It's also kind of amazing the variety of places people put things. I'm leaning towards, if I move the engine controls, side by side like a Cessna, on a sub-panel on the far left side bottom of the panel. But if the center weldment is on the flap drive tube, I might go with moving the flap handle and trim actuator.
I'm going out to the hangar to scout my plane this weekend and figure out how to implement this.

[GordonTurner]

Electric flaps are pretty easy to implement. Might be worth considering.

Gordon

[Bryan Cotton]

On some of the Sonex factory planes, there is a second throttle control. What they do, IIRC, is to mount the standard quadrant on the left. Then there is a cable on the right that loops around under the tank and moves the left hand quadrant. This lets both occupants work the throttle, and of course pedals and sticks. The right seater doesn't have flaps or brakes but for training or letting a buddy have a go that is not all that important.

Edit: can you do something similar but add a second throttle on the left? Then both people could fly left hand throttle, right hand stick and that would be cool.

[karmarepair]

Electric flaps are pretty easy to implement. Might be worth considering.

Gordon

The thought had crossed my mind; with electric flaps and electric trim, I could reach HOTAS (Hands On Throttle And Stick) promised land, but this plane is SO close to flying and I KNOW every mod is at least 100 hours of shop time...at this point, if it's not Safety Of Flight, I'm not fixing it. This one IS, and I want to minimize the hours it will take.