Push/Pull twin Sport Plane

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

rbarnes

Well-Known Member
Joined
Aug 28, 2015
Messages
405
Location
Texas
Me to and believe the front engine will have to be moved for a few inches for the W&B.
Yep, seats forward a couple of inches and the front engine.

Zenith claims 200lbs can be put in the rear jump seat of the standard CH-750SD and the small 150-200hp Apex engines weigh about that much and would be positioned almost directly over that spot in the cabin.

Pair of 200hp Apex engines with SkyTrack PSRU's and feathering electric Airmaster props.

150 hp Apex's would be more than enough, until you lost an engine just after takeoff, then 200hp would be much appreciated.
The 150hp version would be NA though and not require the extra weight and complexity of the turbo and intercooling.

There's also the possibility of using the new 801 SD wing which is larger.
 

Puggo1

Member
Joined
May 19, 2020
Messages
9
hi all,
it's an interesting concept - push/pull aircraft - and definitely has merit over a classic wing mounted twin.

A friend once suffered an rear engine failure in a Cessna 337RG during full power climb out. The climb out rate only dropped 150fpm from his usual climb out rate. It suggests the rear propeller is in very dirty air and rather ineffective.

I wonder is there any flight test reports for a Cessna 337, Rutan Defiant or Adams A500 with either engine shutdown - front or rear? It would make interesting reading to see the effect of fuselage aerodynamic improvements for this engine layout.
 

Tiger Tim

Well-Known Member
Joined
Apr 26, 2013
Messages
4,034
Location
Thunder Bay
I wonder is there any flight test reports for a Cessna 337…with either engine shutdown - front or rear? It would make interesting reading to see the effect of fuselage aerodynamic improvements for this engine layout.
I’ve never flown a mixmaster though nearly all of my professional pilot friends have. They use them for forest fire spotting up this way so it’s a popular summer job. Anyways, every single one of them says that it performs better single engine if it’s the rear engine doing the work. Apparently the rear prop, when powered, actually promotes better airflow around the rear of the fuselage.
 

Vigilant1

Well-Known Member
Lifetime Supporter
Joined
Jan 24, 2011
Messages
6,961
Location
US
hi all,
it's an interesting concept - push/pull aircraft - and definitely has merit over a classic wing mounted twin.

A friend once suffered an rear engine failure in a Cessna 337RG during full power climb out. The climb out rate only dropped 150fpm from his usual climb out rate. It suggests the rear propeller is in very dirty air and rather ineffective.
I'm pretty sure something got garbled in translation, or that rear engine was VERY sick before it failed (so when it finally quit, there was little change in climb rate). If the Skymaster weighed 4000 lbs, it takes about 18 HP of net equivalent effective thrust to produce a climb rate of 150 FPM.

When flying single engine, the Cessna 337 climbs better on the rear engine than the front engine. This is generally attributed to the effect of a running rear engine that reduces drag at the rear cowling (due to low pressure created in front of the prop disk, which helps flow back there).
 
Last edited:

Pops

Well-Known Member
HBA Supporter
Log Member
Joined
Jan 1, 2013
Messages
9,892
Location
USA.
hi all,
it's an interesting concept - push/pull aircraft - and definitely has merit over a classic wing mounted twin.

A friend once suffered an rear engine failure in a Cessna 337RG during full power climb out. The climb out rate only dropped 150fpm from his usual climb out rate. It suggests the rear propeller is in very dirty air and rather ineffective.

I wonder is there any flight test reports for a Cessna 337, Rutan Defiant or Adams A500 with either engine shutdown - front or rear? It would make interesting reading to see the effect of fuselage aerodynamic improvements for this engine layout.
On the C-337, ( all 337's are RG, the fixed gear is the 336 ). You are correct, I think you will find out that the rear engine is the most efficient. If you loose an engine you would rather it be the front engine. Read the POH.
336 is about 300 lb lighter weight and about 15 knot slower.
 

rhbelter

Member
HBA Supporter
Joined
Mar 9, 2015
Messages
16
Location
Carmel CA
10/24/21

Ahoy, Airplane Homebuilders,

I offered my concept of a ‘Push-Pull’ twin airplane, and got a lot of response.

The overwhelming response did NOT like the extension shaft, for many good reasons. The other large concern was engine out climb.

Accordingly, accept the no-shaft base drag, and if this twin p-p sort of airplane becomes popular, someone will develop an extension shaft to reduce drag.

The engine out climb rate problem is easy to solve: Add an engine, (or use two engines of enough power to solve the problem). That yields two different airplanes. I personally prefer to use two AM 2.0 engines @260 hp each, however, below, I show the lower cost, and somewhat simpler three AeroConversion VW based engines, which cost less than one certificated ‘real’ airplane engine, and will easily solve the engine-out problem. I would prefer to be over the Rockies with these three imitation airplane engines than with one ‘real’ airplane engine.

I submit that this solution solves these problems, and still results in a seriously fast sport plane.

A tandem seating configuration became sort of ‘strung-out’, with CG problems.

The airplane: Side by side, pull-push-push. NO rear prop shaft. All easy -- yuhh!!!

Fuselage: Steel truss work. Aerodynamic shape by some suitable method. A composite shell, easily removeable, would be nice to live with.

Surfaces: Pretty much alum 6061, pull riveted. Some members may want carbon fiber. Eventually?

Landing gear: Your call, fixed or retractable. Steel weldment, with air bags. Will be ‘bouncy’, like a spring gear. Add shocks? Either is much lighter than a spring gear. A bit more work, but good fairing of a fixed gear is not easy, and still not as good as ‘not there’. Low-cost. I have done a fair amount of detailed design of the landing gear. The landing gear which I offer is NOT high tech. It is a ‘Blacksmith’s wet dream’.

Actuators: I suggest CO2 or nitrogen, regulated to whatever the highest pressure that components can handle. PLC control.

Engines: AeroVee 80 hp, as shown. The much larger RV10 does more than 200 mph on about the same power with a fixed gear, so this one should do much better. Three AeroMomentum AM15 @147hp are possible, and near 450 hp in a little clean airplane like this will be fast as a sport plane, and climb well on two. The airframe is sized to accept two of the forthcoming AM2.0, and with 520 hp available, will be awesome, and ‘hotted-up’, will likely do well in the Reno Racer’s Sport Class.

Bail out: Not with spinning props back there. Rear prop brakes are indicated, and a forward prop brake may be appropriate. Controllable pitch/feathering props would be nice, but likely not seriously needed in what is intended to be a quite high performance but fairly low cost sport plane.

How to make this happen???

There clearly is enough competence among the membership to do the engineering, detailed design, and component fabrication. IF there is enough interest, there will also be members to devise an organization to bring this airplane to life. NOT me, at 93 years!! Interested members can offer their skills in the various disciplines. If this is successful, there may by some money to be made. ‘Not rich, but less poor’.

IF IF there is interest, my suggestion is for someone to build one prototype. Then, with success, IF there is continued interest, that a limited number of ‘beta’ versions be built, with the possibility of forming a company to produce kits.

My son is ‘untouched’ by any technical education, but is able to set-up, and manage a web site. He has further skills in marketing. He is willing to do this early ‘heavy-lifting. As the project takes shape, Zoom meetings will keep everyone informed, plus an agreed on engineering system -- probably EAA Solidworks. Try for an annual meeting at Oshkosh. Please note my use of ACAD. I have not yet become proficient at the preferable system.





Enjoy /s/ Bob Belter [email protected]
 

Attachments

Vigilant1

Well-Known Member
Lifetime Supporter
Joined
Jan 24, 2011
Messages
6,961
Location
US
A triple engine layout as you've given has some advantages over a twin (obviously, one engine out = just 33% reduction in total thrust rather than 50%). But, it introduces the significant possibility of asymmetric thrust when an engine fails. This requires pilot action (application of proper rudder and aileron and especially not allowing the airspeed to degrade below Vmc). In addition, the application of rudder needed to keep the plane flying straight produces drag, so you'll have somewhat more than a 33% reduction in net thrust (after drag). Blane.c has been a big proponent of 3 engine designs, his posts on the TriMower maybe of interest.

Maybe one or more people will decide to dedicate the many years and dollars needed to bring such a design to reality. That's where the hard work lies. Design-by-committee (to say nothing of more advanced development through prototyping) hasn't produced significant results here on HBA or in the homebuilt aircraft world in general. Ideas are plentiful, but details and hardware are, well, hard.
 
Last edited:

Pops

Well-Known Member
HBA Supporter
Log Member
Joined
Jan 1, 2013
Messages
9,892
Location
USA.
I'm still, still , still waiting for Someone to build the BeetleMaster.
rhbelter-- you must be the oldest person on this site. Makes me feel good (young) at 81 knowing I'm far from being the oldest.
 
Last edited:

Riggerrob

Well-Known Member
Joined
Sep 9, 2014
Messages
2,243
Location
Canada
For a truly silly push-me-pull-you configuration, look at the "Fighter design by Leslie Peel (1944)." over on www.secretprojects.com.
This novel suggestion has two propellers face-to-face in the middle of the airframe. The forward prop is a pusher, while th eaft prop is tractor. they sit in two separate nacelles on the center-line. The two nacelles are connected by diamond-shaped wings. Peel's unbuilt proposal looks like it has load paths too long between the propellers. I worry about the props vibrating relative to each other. I suggested installing a bearing that connects the two prop hubs to minimize relative motion. We wonder how long that bearing would last with two heavy engines trying to vibrate laterally and vertically relative to each other?????????
The same thread includes the purely fictional Bristol Burglar. Burglar looks more practical because it has shorter load paths between the props. Loads are carried outboard by tandem wing only as far as just beyond prop tips where those lateral loads transfer to twin tail booms.
Bottom proposals are configured like canard or tandem wings with props dead center.
Suggestions?
 

delta

Well-Known Member
Joined
May 26, 2011
Messages
2,563
Location
Brookside Utah
This is a better link...

 
Top