An argument in favor of multi-engine design

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

Topaz

Super Moderator
Staff member
Log Member
Joined
Jul 29, 2005
Messages
14,110
Location
Orange County, California
It's interesting seeing the different perspectives. Multi-engine commercial pilot prefers multiple engines - more the better. A glider pilot (me) prefers one simple engine and good gliding capability so that finding a spot to land is much easier. For some, "landing out" is a disaster. For others, "landing out" is an annoyance, and a case of your buddy's favorite beer because he brought out the trailer.

I see the point being made here, and it's fine, I suppose. Me, I'd much prefer the simplicity and low weight of a single engine, and a bit more span, which helps out in everyday flying, too. To each their own, I guess.
 

blane.c

Well-Known Member
HBA Supporter
Joined
Jun 27, 2015
Messages
3,906
Location
capital district NY
I think it boils down to speed. As a high time fighter jet pilot once told me "speed is not your friend" , speed is also expensive. One of the expenses of speed is a higher wing loading with a corresponding reduction in glide distance and a higher landing (impact) speed. If you are thinking cross country cruiser (me) then speed correlates with fuel economy and distance. If you want some reasonable options when you are in close proximity to the earth then multiple engines become a possible solution. This forum is a more cost effective way in both time and money to explore possible options than many other methods.
 

bmcj

Well-Known Member
HBA Supporter
Joined
Apr 10, 2007
Messages
13,395
Location
Fresno, California
[As a high time fighter jet pilot once told me "speed is not your friend" /QUOTE]

Not what I would have expected. The typical fighter pilot mantra is "Speed is Life".
 

Winginit

Well-Known Member
Joined
Jun 12, 2016
Messages
811
Location
x
Offered as an unproven spur of the moment thought. It would seem to me that for a decent looking design something with a twin boom tail design and both engines mounted on centerline would be a good design for a homebuilder. The rear engine could be moumted directly to the fuselage or elevated
slightly for ground clearance. In the event of an engine out, the dynamics of thrust would still be on the centerline of the aircraft and be easier for the pilot to deal with. Something like a modified version of the Sadler Vampire.

https://www.youtube.com/watch?v=gtbk8SllXng
 

blane.c

Well-Known Member
HBA Supporter
Joined
Jun 27, 2015
Messages
3,906
Location
capital district NY
Offered as an unproven spur of the moment thought. It would seem to me that for a decent looking design something with a twin boom tail design and both engines mounted on centerline would be a good design for a homebuilder. The rear engine could be moumted directly to the fuselage or elevated
slightly for ground clearance. In the event of an engine out, the dynamics of thrust would still be on the centerline of the aircraft and be easier for the pilot to deal with. Something like a modified version of the Sadler Vampire.

https://www.youtube.com/watch?v=gtbk8SllXng
Thinking to the extent possible not introducing "both yaw and pitch moments" is probably best. So elevation wise everything pretty close to the cg line. I am thinking twin boom more from an Aesthetics point of view than any other reason. This would place the engines on the booms in tractor configuration, but I am still puzzling over tractor or pusher for third engine. I am thinking it will probably be tractor because I do not want to put it overhead for the above stated reason and the extra weight of reinforcing a rear firewall/bulkhead for 10g's in order to mount it directly behind the cabin may be a deal killer for that arrangement. I like the idea of the look of the third engine in pusher aesthetically it is the better option for me.
 

bmcj

Well-Known Member
HBA Supporter
Joined
Apr 10, 2007
Messages
13,395
Location
Fresno, California
Offered as an unproven spur of the moment thought. It would seem to me that for a decent looking design something with a twin boom tail design and both engines mounted on centerline would be a good design for a homebuilder. The rear engine could be moumted directly to the fuselage or elevated
slightly for ground clearance. In the event of an engine out, the dynamics of thrust would still be on the centerline of the aircraft and be easier for the pilot to deal with. Something like a modified version of the Sadler Vampire.

https://www.youtube.com/watch?v=gtbk8SllXng
Yes, an excellent configuration for a designer to work with, but possibly less than optimal for the passengers who are likely sitting in a short fuselage between two nearby noisemakers.
 

Sockmonkey

Well-Known Member
Joined
Apr 24, 2014
Messages
1,880
Location
Flint, Mi, USA
Doing a tandem wing lets you keep both close to the centerline and makes it easy to use a cross-shaft for one engine to drive both props if you feel the need.
 

Winginit

Well-Known Member
Joined
Jun 12, 2016
Messages
811
Location
x
Of course if money is no object you could use 3 of the small Turbojet engines like Sonex uses. A mere $55K apiece.
 

timberwolf8199

Well-Known Member
Joined
Sep 3, 2011
Messages
279
Location
Grand Rapids area, MI, USA
It would seem to me that for a decent looking design something with a twin boom tail design and both engines mounted on centerline would be a good design for a homebuilder.
I've often thought that a P-38 built in reverse would be an interesting ride. That is, push-pull engines on the center pod and cockpits on the booms. Unfortunately the separation of passenger from pilot is not likely to be popular and asymmetric loading for pilot only operation have always seemed like big enough issues to prevent me from letting it get beyond a passing thought.
 

blane.c

Well-Known Member
HBA Supporter
Joined
Jun 27, 2015
Messages
3,906
Location
capital district NY
Yes, an excellent configuration for a designer to work with, but possibly less than optimal for the passengers who are likely sitting in a short fuselage between two nearby noisemakers.
Isn't eventual deafness for pilots and their friends and family's just a given anyway? Seriously though, how do you significantly lessen the decibels of the propulsion package without adversely affecting performance.
 

blane.c

Well-Known Member
HBA Supporter
Joined
Jun 27, 2015
Messages
3,906
Location
capital district NY
I've often thought that a P-38 built in reverse would be an interesting ride. That is, push-pull engines on the center pod and cockpits on the booms. Unfortunately the separation of passenger from pilot is not likely to be popular

Depends on how obnoxious your passenger is ... could be very popular for some ... like a mother-in law apartment.
 
Top