Would you be interested in some form of back-up propulsion for your piston single? If yes, how much would you be willing to pay for it?

How much would you pay to have a back-up?

  • This is a dumb idea, I'll never want any back-up. Engines are reliable enough.

    Votes: 23 74.2%

  • 10-20% of engine overhaul cost.

    Votes: 0 0.0%

  • 21-30% of engine overhaul cost.

    Votes: 2 6.5%

  • 31-40% of engine overhaul cost.

    Votes: 3 9.7%

  • 41-50% of engine overhaul cost.

    Votes: 2 6.5%

  • 51-75% of engine overhaul cost.

    Votes: 1 3.2%

  • 76-100% of engine overhaul cost.

    Votes: 0 0.0%

  • Even more than what it would take to overhaul the engine, I would really like the added safety.

    Votes: 0 0.0%
  • Total voters
    31
Salty said:
I can't even imagine the complexity of systems management of this system. You think people won't kill themselves by operating your contraption incorrectly? Is it "pull the knob and it's full throttle until it runs out of fuel? Or are you going to allow for throttle control? Will that control use the same throttle as the primary engine? If so, now you're adding complexity that could cause failure to the primary system. Etc, etc, etc.
Click to expand...
Good questions, but you already got to the right answer for an emergency situation - pull lever, get fixed power, when landing area (hopefully runway) is made, turn it off and land.
I really value your opinions and questions on this, since you have first-hand experience.
 
The other factor is that more than a third of engine failures occur during the takeoff phase. I suspect the backup power system probably won't be enough to climb, and THAT'S going to be sporty. More likely to stall on the way around, which DOES kill people.

Ron Wanttaja
 
Always nice to have your input. Valid point, there would have to be at least some level of excess power to allow a small amount of climb at Vy. It's also a safety feature to allow recovery if you're (slightly) on the back side of the power curve.
 
Trying to compensate for an engine out in a twin? - Half of them will be in someone else's airplane.
 
How are you planning to couple it to the prop and decouple the prop from the dead engine?

Or do you want it to provide direct thrust? Then you have an entirely new load path and center of thrust for the plane and retrofits become very complex ("remove plane's N#, install new airframe, reattach N#").
 
To be clear, he's talking about strapping a mini jet engine to the plane.
 
Salty said:
To be clear, he's talking about strapping a mini jet engine to the plane.
Click to expand...

That's what I was afraid of. New load path and additional structure, new thrust line, need clear path for the jet exhaust gases, etc., etc. And not being able to throttle the thrust would be a serious problem.
 
Half Fast said:
New load path and additional structure, new thrust line, need clear path for the jet exhaust gases
Click to expand...
1709829653166.png

That exhaust is angled down for a couple reasons. Load path for sustained use vs emergency use has different design considerations.
 
AV8R_87 said:
It will fly a 1000-lb plane at 210 kts, in this application it needs to keep you in the air at 80kts or so. That's a lot less drag to overcome.
Click to expand...
Nope. You have to haul around the cooling drag for an entire 300hp engine. plus a windmilling prop, plus 3x the weight, plus the sonex was engineered to have a turbine engine and will be more efficient. Your assumptions are flawed.
 
AV8R_87 said:
Load path for sustained use vs emergency use has different design considerations.
Click to expand...

Certainly, but there have to be test flights post installation and pilot training (possibly recurrent), and landing loads have to be considered and that's every time you land. Not to mention how mounting location may effect aircraft CG location and flying characteristics.
 
This just happened yesterday 3/6/24
Two people were on the Cirrus SR-22 at the time and suffered no injuries, according to the Bellevue Fire Department (BFD). They were able to climb out of the plane when it landed
Click to expand...
 
In the 20s/30s, the Soviets had brilliant idea: They strapped a fifth engine to their four-engine bomber. Its sole purpose was to run the supercharger that they forgot they needed.

I think that puts your idea into the same tier as some early Soviet designs...
 
wanttaja said:
Not, ummm, impossible. Back in the '80s, a guy I worked with had a ballute concept (concatenation of balloon and parachute) for satellite re-entry. The capsule or whatever would be behind the ballute, which faced into the re-entry plasma. It was actually cooled by the exhaust from a rocket engine facing forward.... the rocket exhaust was cooler than the plasma. So, conceivably, you could have a hot-air balloon inflated by a jet engine.

View attachment 126356
The man's name was Doctor Dana Andrews (same as the actor). The movie "2010" used this concept to slow a spacecraft around Jupiter, and Andrews' name is listed in the credits.

Ron Wanttaja
Click to expand...
A similar concept was successfully tested a few years ago, cooling rocket engine not required.

www.space.com

NASA's inflatable flying saucer aces Mars heat shield reentry test

LOFTID soared into space and back again Thursday (Nov. 10), safely splashing down in the Pacific Ocean on a crucial test of aeroshell technology for eventual human Mars missions.
www.space.com www.space.com
 
Klaus M said:
This just happened yesterday 3/6/24

Click to expand...
Funny you mention that. The BRS also took a lot of hate and vitriol from the crowd that saw it like a way of chickening out instead of flying the airplane all the way to the scene of the crash. A mindset that seems to persist to this day.
2-Bit Speed said:
I think that puts your idea into the same tier as some early Soviet designs...
Click to expand...
Oh, I've seen much dumber Soviet ideas, and the US has its fair share of ugly ducklings.

Half Fast said:
Certainly, but there have to be test flights post installation and pilot training (possibly recurrent), and landing loads have to be considered and that's every time you land. Not to mention how mounting location may effect aircraft CG location and flying characteristics.
Click to expand...
I agree, this wouldn't be a case of attaching it to the airframe with four self-tapping sheetmetal screws and hoping for the best. Careful design (especially with regard to center of thrust and CG placement) would probably mitigate most of the flying characteristics concerns. It would still be a decent-sized certification flight test effort.
 
Mtns2Skies said:
Look at the thrust on that. Ain't gonna cut it for a 3000+lb airplane.

Go try to fly your plane at 35% power. Hint (Economy cruise is your most efficient, any deviations from that and you get less efficient)

And then immediately after that sign up for physics 101.
Click to expand...
I agree, but I'd also argue that Economy Cruise is a purely a marketing number, and L/Dmax is most efficient, which is more like Vy and slower yet.
 
Mtns2Skies said:
Look at the thrust on that. Ain't gonna cut it for a 3000+lb airplane.

Go try to fly your plane at 35% power. Hint (Economy cruise is your most efficient, any deviations from that and you get less efficient)

And then immediately after that sign up for physics 101.
Click to expand...

From my POH; 36% will keep me in the air going 100+ knots at MGW, since best glide speed is 91 knots then 35% will definitely keep me in the air, I think even 30% will.
 
Mtns2Skies said:
Oh, you don't give yourself enough credit ;)
Click to expand...
Nice try. F- because you didn't pay attention to the rules.
Mtns2Skies said:
Nope. You have to haul around the cooling drag for an entire 300hp engine. plus a windmilling prop, plus 3x the weight, plus the sonex was engineered to have a turbine engine and will be more efficient. Your assumptions are flawed.
Click to expand...
Cooling drag, do the math, you'll find out it's not that much at the speeds we're talking about. Also, all of that is already accounted for in the thrust needed to keep the plane airborne. Hopefully you remembered to pull the blue knob and stop the prop before whatever caused your engine to go on strike drains all the oil out of it.

Speaking of my assumptions being flawed, here's some more data that lines up with my flawed assumptions. Feel free to provide data that disagrees.

Airspeed for minimum sink Vmins = 63.5 mph
Minimum power required for level flight THPm = 41.06 HP
Minimum drag Dmin = 210.1 lb
Minimum sink rate RSmin = 589.1 fpm
Maximum lift-to-drag ratio LDmax = 10.94
Lift coefficient at minimum sink CLmins = 1.29
 
JATO bottles! Rocket up to 15,000 feet and your 10 minutes is glide time.

Good luck getting the STC...
 
I think everyone is interested in that but aside from a twin the only workable thing would seem to be a parachute.
 
Dana said:
JATO bottles! Rocket up to 15,000 feet and your 10 minutes is glide time.

Good luck getting the STC...
Click to expand...
Someone on this board will tell you they can install them as a minor alteration...
 
Dana said:
JATO bottles! Rocket up to 15,000 feet and your 10 minutes is glide time.
Click to expand...
The problem with JATO bottles is the short burn time. They're (mostly) intended to get the plane off the ground quickly; any major altitude gain is a bonus.

Don't forget the issues with the exhaust; unless you've got blowaway panels, the JATO unit have to be mounted to the outside of the airplane to keep from scorching the tail. Could put it on a deployable arm (like a RAT), but then the arm needs to withstand the thousand-pound or so thrust. So it's not just the weight of the rocket/jet itself.

Finally, there'll be a CG issue with rocket-type JATO bottles if they use solid propellant and are located any distance aft. Hundred pounds? Two hundred pounds? Of propellant gone in five or ten seconds. If that bottle's in the tail, you're going to be facing a sudden nose-heavy situation.

With conventional jet-engine JATO, you could at least put the fuel closer to the CG...though, then, you need appropriate fuel lines running to wherever the jet is. Hardly an STC situation.

Ron Wanttaja
 
IMG_6036.jpeg

Plumbing one of these in would solve the 10-minute problem for a good number of engine failures in flight. Might need two for a twin, to get 10 minutes, depending on the engines.
 
I think the closest practical solution for this would be a hybrid system, with 10 minutes of battery reserve if the IC engine quits. Probably already on someone's drawing board. Practical? Maybe. I still think an airframe chute is the best choice as it gives protection for a whole host of other failures during which backup propulsion is useless.
 
Dana said:
JATO bottles! Rocket up to 15,000 feet and your 10 minutes is glide time.

Good luck getting the STC...
Click to expand...
If you hadn't realized it, my picture of the Ercoupe is a zero-takeoff role JATO launch.
 
You must log in or register to reply here.
Back
Top