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Aux power - thrust

A type rating is required in a specific make and model of aircraft if the aircraft weighs more than 12,500 lb (5,700 kg) at takeoff or is powered by one or more turbojet engines.

Might make for an interesting discussion with the FAA. :rolleyes:

John Clark ATP, CFI
FAAST Team Representative
EAA Flight Advisor
RV8 N18U "Sunshine"
KSBA
 
FAA :mad:

Over here we have an "unregulated" class (google 'SSDR') and an RV builder built & flew a (twin) jet powered one. No safety oversight, but needs to be registered, insured and pilot microlight licensed.

1st flight

Not too practical, but in March this class is expanded to more realistic weights...
 
Bolt 8 of them to the wings in 4 little pods and call it the RV-52. Quick google search revealed that the trust of 8 of these is equivalent to approx 150hp:D
 
To further John's point, Sonex had/is having all kinds of fun with the FAA with their SubSonex, specifically because it's an E/AB with a turbine. It's in this month's Experimenter.

Would be immensely fun though, even if only for the start-up sound. Now combine that with some good timing of starting your normal piston engine, and freak out everyone at HAO thinking it was a turboprop. :)
 
David Z said:
Bolt 8 of them to the wings in 4 little pods and call it the RV-52. Quick google search revealed that the trust of 8 of these is equivalent to approx 150hp:D
Click to expand...

I could not hold off from buying a Vans kit that had 4 of these under each wing! Its fun to think about it anyway. You could pull it out, go fly it, and then hide it from the FAA back in the cave hangar like the old "Airwolf" TV show.
 
calculated

I calculated roughly 200 lb thrust is provided by my 160 HP engine at 150 kt cruise at 9K. How much thrust would be required to maintain level flight at best glide speed? This turbine produces 66 lb thrust. It seems the micro turbine capability is growing rapidly.

Can you imagine the throttle quadrant for an RV-52?

I wonder if the aerobatic guys could use these as aux thrust?
 
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The Catch

As much fun as this speculation is, a little reality check is in order. The ongoing problem with turbine power in small GA aircraft is that the engines do not "scale" well. That is, the fuel burn does not go down with the size/power of the engine. The engine in your example burns 11.25 gallons per hour, so to get the needed thrust you would need 4 engines burning 45 GPH of heavy jet A. But it would sound cool!

John Clark ATP, CFI
Aviator & Gearhead
FAAST Team Representative
EAA Flight Advisor
RV8 N18U "Sunshine"
KSBA
 
I wanted 8 little jets.

John Clark said:
The engine in your example burns 11.25 gallons per hour, so to get the needed thrust you would need 4 engines burning 45 GPH of heavy jet A. But it would sound cool!
Click to expand...

I was planning on putting 8 of these on the plane, hence the "RV-52". At 90 GPH, there isn't enough fuel for even VFR reserves. Doesn't it suck when reality gets in the way. :D
 
I was thinking about the fuel scaling problem when watching the UK video. I wonder if that was about the limit of his fuel. Fun toy but that's all maybe.
 
extended glide

it seems they also have a model rated at 88 lbs thrust. what if it could run on 100LL so no additional fuel needed except maybe some oil to mix inline. estimate complete weight of mounted unit = 15 lb. minimal drag of unit with bullet nose cone and trail cone that are jettisoned prior to start, about the same drag of a external mounted camera. example, you're over lake Michigan and don't want to get your feet wet if you have an engine out. I believe 88 lbs thrust could sustain flight in a 9A in ground effect.
 
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There was an airshow act with a couple of small turbines mounted in the wing tips, saw it at and airshow at Lake Tahoe about 10 years ago.

The main reason for the tip mounting was smoke generation as I recall, but he could also taxi with just them----------was funny to see him land, shut off the engine, and continue to taxi on to the parking area with the prop stopped.

I think the plane was a Giles or a One Design?? I have no idea if he is still performing with this setup.
 
turbine mounting position

mounting two of them, one in each wing tip, could be an option because you could fair them in nicely with the wing tip but may suffer from asymmetric thrust if one failed. what about one turbine mounted as far aft as reasonable in the center so the thrust is in line and no occupants are in the rotor burst zone?
 
It would be kinda neat to have a few extra pounds of thrust available for augmenting takeoff from short, backcountry airstrips with high density altitude. That would truly be "JATO". :D
 
John Clark said:
A type rating is required in a specific make and model of aircraft if the aircraft weighs more than 12,500 lb (5,700 kg) at takeoff or is powered by one or more turbojet engines.

Might make for an interesting discussion with the FAA. :rolleyes:

John Clark ATP, CFI
FAAST Team Representative
EAA Flight Advisor
RV8 N18U "Sunshine"
KSBA
Click to expand...

Is that true if it is a motor glider?

IIRC at least 4 of these 220 lb thrust Caproni A-21-SJ sailplanes were imported to the US.

http://www.sailplanedirectory.com/PlaneDetails.cfm?planeID=413
 
Does the phrase "or is powered by one or more turbojet engines" mean "powered ONLY by one or more turbojet engines"? Because I don't remember reading the the Waco biplane with the normal radial PLUS the bottom-mounted jet needed a type rating. (Maybe multi-engine centerline thrust?)
 
motor glider

perhaps this application could be classified as either motor glider for engine out condition or thrust augmentation on center line. the first application for safety the second for performance. hopefully, a turbine rating is not required.
 
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How about a couple of hydrogen peroxide engines. There was a guy at KOSH a couple of years ago with this type of engine on his gyro copter. Each had an output of around 120 pounds of thrust. That would give you a ice boost on take off.
 
B36 Wiki

The B36 jet engines used avgas

Beginning with the B-36D, Convair added a pair of General Electric J47-19 jet engines suspended near the end of each wing; these were also retrofitted to all extant B-36Bs. Consequently, the B-36 was configured to have ten engines ("six turnin' and four burnin' ", as characterized by Airmen Magazine), more than any other mass-produced aircraft. The jet pods greatly improved takeoff performance and dash speed over the target. In normal cruising flight, the jet engines were shut down to conserve fuel. When the jet engines were shut down, louvers closed off the front of the pods to reduce drag and to prevent ingestion of sand and dirt. The jet-engine louvers were opened and closed by the flight crew in the cockpit, whether the B-36 was on the ground or in the air.[23] The two pods with four turbojets and the six piston engines combined gave the B-36 a total of 40,000 hp (30 MW) for short periods of time.[24]

http://en.wikipedia.org/wiki/Convair_B-36

http://www.nmusafvirtualtour.com/media/062/B-36J%20Engineer.html

http://www.nmusafvirtualtour.com/full/tour-std.html
 
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New Mexican, Bob Carlton probably has as much experience with this stuff as anyone. I remember having a conversation with him about the type rating issue but I have a poor memory and the links on the web are dead. I think it came down to working with the feds and getting a waiver.
 
Sasquatch type rating

Here's what John had to say when I asked about the necessity of a type rating in his new plane:

"Damon, no type rating required as it was certified as Experimental Exhibition group 2. There are different groupings of Exhibition and the jet is not considered a "primary" power plant. Basically the grouping tell the Fed which limitations to apply when drafting the limitations for the airplane. It was a really complex process to get the paperwork for this airplane."

So it seems to me if you wanted to add a turbine to your RV, you might have to re-certify, and it would not be a simple process.
 
FAA

I spoke with the FAA today and reviewed the concept. They believe it is doable with a Letter of Authorization. No multi-engine or turbine rating required since the turbine is on center line. The first step is to fly with a mockup to determine drag and handling characteristics. Insurance is possible and they can work with me from AIG. Vans said they don't know what thrust is required at best glide speed.
 
n5lp said:
New Mexican, Bob Carlton probably has as much experience with this stuff as anyone. I remember having a conversation with him about the type rating issue but I have a poor memory and the links on the web are dead. I think it came down to working with the feds and getting a waiver.
Click to expand...

An update on this from the January 2014 issue of Sport Aviation where Bob does a report on the Subsonex JSX-2 jet powered kit airplane. "As of this writing, all pilots of type certificated turbojet airplanes require a type rating. Lacking a type certificate, experimental jets require an LOA (letter of authorization) in lieu of type rating. Since new experimental jets are somewhat rare, the requirements for an LOA in a new experimental jet are a bit ambiguous. Suffice it to say that some jet experience together with some sport aircraft experience will be required."

By the way the numbers are max speed 213 knots, cruise at 17,500 MSL 177 knots. With 44 gallons of fuel he says you can go about 350 nautical miles in 3 hours.
 
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Sean DeRosier

There was an airshow act with a couple of small turbines mounted in the wing tips, saw it at and airshow at Lake Tahoe about 10 years ago.
Click to expand...

That was Sean DeRosier of Fairfield, CA in a One Design he and his father built. He would taxi with the engine off using the turbines. I believe he told me they had 50 LB of thrust each. He was sponsored by Sammy Hagar's Cabo Wabo tequila. Sadly he died doing his thing in San Diego on 10/15/04.
 
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Mike, thanks for the info, that is the one I remembered.

Google found a bit of info, including this photo.

w_wing-tip-smoke-derosier.jpg


As I mentioned earlier, tip turbines were used to make smoke--------lots of smoke:D http://www.youtube.com/watch?v=tnRWDXIhj7g
 
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goal

That's a cool picture and good smoke!

The goal would be to get down safely if engine out. For normal flight the turbine would be blanked off with bullet nose and have a trailing cone to minimize drag to about 5 kt or less. The nose and trailing cone could be made of styrofoam and jettison before start but I'm not sure if that is acceptable, dropping stuff. For example, you’re over Lake Michigan and have an engine out and don’t want to get your feet wet. 30 minutes of flight time anywhere in the US should be able to get you to a suitable landing spot. An alternate approach to the airplane parachute.
 
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Micro Turbine Starting

Steve Melton said:
That's a cool picture and good smoke!

The goal would be to get down safely if engine out. For normal flight the turbine would be blanked off with bullet nose and have a trailing cone to minimize drag to about 5 kt or less. The nose and trailing cone could be made of styrofoam and jettison before start but I'm not sure if that is acceptable, dropping stuff. For example, you’re over Lake Michigan and have an engine out and don’t want to get your feet wet. 30 minutes of flight time anywhere in the US should be able to get you to a suitable landing spot. An alternate approach to the airplane parachute.
Click to expand...

The real issue that you may have with this idea is that I don't think these micro turbines start up very reliably which would not be good for an emergency device. I know that Yves Rossi occasionally has trouble getting all four of his engines to light off before flights with his flying wing.
 
motor assisted air starts

agree, starts are a challenge. higher altitude starts are more difficult. OAT is a factor along with airspeed. need to meter the correct fuel for starting and monitor the start and make fuel adjustments as necessary. at least motor assisted starts are easier than a windmill start and cannot do windmill start easily with a radial compressor.

starting behind a windmilling prop is another concern from LAMPSguy (below) but best to keep the turbine on center line and occupants and critical airframe hardware clear of the rotor burst zone.
 
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Couple issues

First, depending on how close they are to the prop, there could be some possible compressor stall issues from the prop causing the intake air to be disturbed.

I was "dreaming" about this as a "JATO" idea, put near the wing roots, small couple gallon tanks in each wing just for the extra thrust on takeoff. But then, I think it would be much lighter/easier to just get a high powered rocketry guy to get a couple rocket engines and just make a REAL JATO!

Then, I got real crazy and was thinking (wouldn't work in real life) to arrange maybe 7-8 of them radially around the nose, basically in place of each of the jugs in a radial engine...cowl would look REALLY cool. Maybe have a prop "just for looks", it starts spinning once the relative wind passes through it!

Not practical, but a fun exercise for the brain...would look cool in a comic/movie where reality/physics don't matter!
 
I have a friend in South Australia who modded an ASW20 sailplane to carry three microturbines.

asw20.jpg


The two side engines retract into the fuselage behind carbon fiber doors when they're shut down. The top engine is enclosed by an aerodynamically faired pod. It's far enough aft that it makes very little difference to the glide ratio.

Best climb with three engines is at about 45 degrees deck angle at 105 knots. Gets him from sea level to 10,000' in about three minutes. Then he shuts down and glides for 90 km or so.

When he starts getting low he fires up the centre engine. Gives him about 2000' per minute climb at about 90 knots. Once it's back to 10,000 he can shut down again and get another 90km.

50 litres fuel capacity in wing bladders gives him a range of about 500km in still air. Obviously more if he takes advantage of thermals along the way.

The ECU is pretty straightforward: One switch to extend and start the engines; turn it off and they'll automatically run through a cooldown cycle (pulsing the starters as necessary to keep them rotating until they're cold) then retract. The power control is a potentiometer that he's fitted with a volume knob from an old stereo, so it's the only airplane I've ever seen that has a throttle control that runs from zero to "loud" :)

- mark
 
ASW20

Innovative doors on the inlet to reduce drag on the center turbine. These doors also provide some inlet protection. Similar concept to the B36 jet pod doors. B36 jets burned avgas and had water injection.

Perhaps for takeoff the engine could be operating at idle power so max power would be available immediately if needed. After becoming airborne, shutdown the turbine and close the doors. The downside is the overall diameter is larger and increases drag and moves away from the goal of just getting down safely.

DSC00534s.jpg


DSC00540s.jpg


B-36_engines%2C_Richie.jpg




The turbojets on the market are low tech with low pressure ratios (<4) but are cost effective for the radio control market they serve. Could there be a new market for light aircraft emergency power that would justify better turbines for more expense that would have more power and be more efficient? Or can the current turbine be optimized for one time use at overboost power for 30 minutes then replace? If the goal is to get down safely then the later is the better choice. We need a design that's cheap, lots of power, one time use then replace, that runs on avgas. These turbines would only be put into service in emergencies and rarely. What a business, sell a product that is rarely used. Great!

jetcat_28open29.jpg
 
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Steve Melton said:
The turbojets on the market are low tech with low pressure ratios (<4) but are cost effective for the radio control market they serve. Could there be a new market for light aircraft emergency power that would justify better turbines for more expense that would have more power and be more efficient?
Click to expand...

On gliders we already have such an "emergency" system, it's called a "turbo" or a sustainer is probably the correct term, and it's fairly common. It is a small retractable two stroke engine with a small diameter propeller. It cannot be used for self launching as the thrust is way too low, but it has enough thrust to sustain flight. A self launcher must have a larger propeller and a larger engine; more weight, more cost, more space, more everything. There have been some development of electric turbos, but so far nothing can really beat the simplicity, weight and price of a small air cooled two stroke.

RTEmagicC_c5b92af6f3.jpg.jpg


I guess a small turbine would be a much more compact solution, but also much more complicated and way more expensive. A 400N thrust JetCat is already more than 10 thousand dollars, and you consider this "low tech". A "real" aircraft turbine like the TJ-100 (also used on some experimental gliders and the Subsonex) is 60 thousand dollars http://www.desertaerospace.com/turbines.html

It really is a cost/work/wight problem in terms of MTTF. A turbine emergency system is bound to cost 50-100 thousand dollars, and what you get is an extremely complex system of turbines and ECUs. Wouldn't it be better to use those money to increase the MTTF of the engine? For that amount of money (+ the main engine) you could even get something like this:
tp100_start.jpg

http://www.pbsvb.com/turboprop-engine-tp-100-and-turboshaft-engine-ts-100
 
3D metal printing

Hey, I like that turboprop! 250 Hp. But why is the pilot giving the middle finger in the test flight picture?

What if the cost of the turbine could be made very low by using 3D metal printing? By using 3D metal printing it is possible to mfg very complex shapes at low cost. The turbine would be designed for maximum power for short duration, 30 minutes, operating on avgas. After one time emergency use the turbine would be replaced. I believe a similar turbine to the jetcat could be printed in four components and would include integral fuel passages.

random sample from the internet

Turbine_3D_printing.jpg
 
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Turbine

With the extreme temp environment the turbine has to operate in, they have to be mfg out of high cost metals. I don't think a "printer" mfg part would last a minute. if its spinning 40,000 rpm when she lets go, the buzz saw effect would be spectacular. I guess the next backup device would be a parachute unless you were in inline with the rotor axis....

I don't know what the rpm range of these small turbines are but apu's are typically in the 30,000 to 40,000 range. Experimenting with rotor material at this rpm would require a nice test cell and some $$.
 
How about applying a bit of KISS technology here???

Pulse jets are designed to work on gasoline, and are low in cost and weight,

Lots of plans available too---------or spend $100 to get a working one and reverse engineer it up size to get something you need. Your idea of drag reducing front fairing will work well here as well.

Imagine having a few of these hanging under the wing, and a military style paint job:D

34247main2.jpg


http://www.hobbyking.com/hobbyking/...gine_34_red_head_34_with_ignition_system.html
 
pulse jet

yep, pulse jet was a first choice. however, it seems they are hot, loud, can be unstabile and go boom or have a lot of flame, inefficient for the amount of thrust they produce.
 
Steve Melton said:
yep, pulse jet was a first choice. however, it seems they are hot, loud, can be unstabile and go boom or have a lot of flame, inefficient for the amount of thrust they produce.
Click to expand...

A pulse jet is loud? You, sir, have the gift of dramatic understatement :D
 
Steve Melton said:
they are hot, loud, can be unstable and go boom or have a lot of flame
Click to expand...

Well, for an emergency use only, these drawbacks become known as "acceptable tradeoffs"

If you were looking at day-to-day operation they are probably a bad choice.

TANSTAAFL
 
Reality check time. The majority of engine stoppage events in flight is related to fuel starvation. Even at the most basic level of analysis it is obvious that simply ensuring you have adequate fuel before your flight across Lake Michigan will essentially erase the "requirement" for this overly complex safety solution. And if one is simply determined to build something to address this "problem", then adding extra fuel will be far and away a better solution than integrating a retractable turbine engine to an RV.

Steve, what does your signature line say?

I don't mean to be a wet blanket if this is simply a lighthearted "what if" type discussion, but this appears to be a serious attempt to solve a perceived problem with aircraft engine reliability. As such, we should step back and see if we are in fact solving a problem in the most efficient way, or simply trying to find a problem that this little jet engine can "solve".
 
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