Wild DoubleEnder bush plane - photo

[Altair]

Wild DoubleEnder bush plane powered by two engines in a push-pull configuration.

Fullsize image: https://diqn32j8nouaz.cloudfront.net...e_fullsize.jpg



Previously:

airplane short takeoff/landing records
Backing in a plane with a reversible propeller - video
Vertol VZ-2 V/STOL research aircraft - photo
Boeing YC-14 - photos and video
Bell Boeing V-22 Osprey unfolding - GIF and photos

[nova_robotics]

I was always told wheels hitting water would cause enough drag to make an aircraft flip over. Can this weird little nugget pull it off?

[piper184]

that all depends if you are producing enough thrust to overcome the added drag of the water interface.

[nova_robotics]

that all depends if you are producing enough thrust to overcome the added drag of the water interface.

I don't think that's correct. Thrust acting to push the plane forward from up high, and drag acting to pull the plane backwards acting down low at the wheels will cause a net torque that causes the plane to nose-down. It's not just a sum of forces pushing forward versus forces pushing backward. It's why the 737 Maxs were a failure. They moved the engines up higher which caused a net torque on the airframe that dipped the nose down as thrust was applied.

[FEM2008]

I don't think that's correct. Thrust acting to push the plane forward from up high, and drag acting to pull the plane backwards acting down low at the wheels will cause a net torque that causes the plane to nose-down. It's not just a sum of forces pushing forward versus forces pushing backward. It's why the 737 Maxs were a failure. They moved the engines up higher which caused a net torque on the airframe that dipped the nose down as thrust was applied.

I see that the flaps are down but I cannot see the elevator very well. From the shadow, it might actually be down, which would aid in toppling the plane over. However, in the video link below, at about 3:37 mark, you can see the pilot alternating between up and down elevator a couple of times to keep the nose up after the wheels hit the water. It definitely looks like a risky maneuver, but bush pilots are some of the best around.

[metric_taper]

I don't think that's correct. Thrust acting to push the plane forward from up high, and drag acting to pull the plane backwards acting down low at the wheels will cause a net torque that causes the plane to nose-down. It's not just a sum of forces pushing forward versus forces pushing backward. It's why the 737 Maxs were a failure. They moved the engines up higher which caused a net torque on the airframe that dipped the nose down as thrust was applied.

Just the opposite, the engines being extended well in front of the center of lift causes the nose to be pushed up. MCAS would engage and push the nose back down to prevent stall.
With engines at high level of thrust, this would cause an overspeed of the airframe.

It's frustrating, I worked for the company that was the subcontractor to Boeing (I was retired when all this happened, but us retiree's talk). The real problem was that Boeing marketing drove all the decisions. They didn't want to require any pilot training for this major change to the airframe. Part the the failure was a screwup with the implementation on the subcontractor side (failure to display miscompare, as they thought this was part of the optional software to be purchased by the end aircraft owner). As well any real intelligent systems engineering 'left the building' on the Boeing side. Computer science was the main design input on the subcontractor side (and they lack the physics and math training, and failed to understand the requirements specification document). And these folks, did not have the system experience to see the single point failure of an AOA driving the system into a dive. There are two AOA sensors, and the system should have screamed with a miscompare, of the two. That was masked in the display as that is where the implementation error really was injected.
I still don't understand why airspeed, and attitude were not convolved in the decision to push the nose down, as clearly the AOA vanes were prone to damage and failure. And in all my avionic's training, critical systems (to safe flight and landing) require triple redundancy, and of dissimilar designs, or a design that is verified from all possible faults and their resulting influence to "continue safe flight and landing".
In the end, the crashes were really the result of pilot error, that wanted to keep the automatic pilot engaged, and not hand fly the aircraft.

[piper184]

I don't think that's correct. Thrust acting to push the plane forward from up high, and drag acting to pull the plane backwards acting down low at the wheels will cause a net torque that causes the plane to nose-down. It's not just a sum of forces pushing forward versus forces pushing backward. It's why the 737 Maxs were a failure. They moved the engines up higher which caused a net torque on the airframe that dipped the nose down as thrust was applied.

Not quite accurate. I don't know about the 737 Max, that is out of my range. What you have to consider is center of thrust vs. center of drag. Any misalignment will cause rotational forces. All aircraft have the center of thrust above the wheels. However, you must combine the drag from the wheels and the total drag of the aircraft to plot an accurate center of drag. The difference between center of drag and center of thrust is usually compensated for by control surfaces (elevator). I fly an ultalight with a pusher engine mounted high above the wheels and well behind the center of lift. When all the forces equal out it flies straight and level. When one force gets out of balance you compensate with another force. Climbing, descending, or turning are all unequal forces that act in a controlled way to accomplish a particular maneuver just as this pilot is washing his wheels by keeping all the forces in balance. The tricky part is not to lose that balance in a direction that leads to disaster. I have seen the results of pilots who thought they were more talented then the really were. Really ugly results.

[Saltfever]

The tail has tremendous elevator authority. At 4:01 you can see him lift the tail off the ground standing still! Many tail dragers need some forward velocity to do this. It has two tandem engines thus assuming CG is located somewhere between them. Probably quite a bit BEHIND the center-line of the wheel axles. Tail dragers have the CG behind the axles so the tail will sit on the ground. As mentioned, wheel drag would create a turning moment about the CG but some of it is attenuated by the distance from the CG. Also mentioned, pitch stability needs to offset that moment. Look carefully at 3:37 and 3:38. As the wheels make initial water contact there is only a slight UP deflection of the elevator. However, milliseconds later you will see the plane LIFT from the hydroplaning wheels as they start to dig in. At that exact time he aggressively applies UP elevator. With the tremendous elevator authority, and the UPWARD acceleration from the hydroplaning wheels, everything is in harmony. :-)

[FEM2008]

The tail has tremendous elevator authority. At 4:01 you can see him lift the tail off the ground standing still! Many tail dragers need some forward velocity to do this. It has two tandem engines thus assuming CG is located somewhere between them. Probably quite a bit BEHIND the center-line of the wheel axles. Tail dragers have the CG behind the axles so the tail will sit on the ground. As mentioned, wheel drag would create a turning moment about the CG but some of it is attenuated by the distance from the CG. Also mentioned, pitch stability needs to offset that moment. Look carefully at 3:37 and 3:38. As the wheels make initial water contact there is only a slight UP deflection of the elevator. However, milliseconds later you will see the plane LIFT from the hydroplaning wheels as they start to dig in. At that exact time he aggressively applies UP elevator. With the tremendous elevator authority, and the UPWARD acceleration from the hydroplaning wheels, everything is in harmony. :-)

Thank for the explanation. It's pretty amazing take off really. Less than 30 ft and it was airborne. Another plane that does the same is the Carbon Cub. If anyone is interested, here is another video that shows amazing performance for a small plane. Tremendous use of the elevator to balance the ridiculously short landing at time mark 1:18.

[diesel8mech]

engines being mounted at this angle is what allows aircraft to have such short take off also allowing for this type of landing . Used to fly a super cub with tundra tires could do this for short distance on water as long as I had full up elevator and flaps at full down. First time I did it thought I would have to have seat cover surgically removed from my ass LOL