LSA limitation re takeoff power for 5 minutes

eetrojan

eetrojan

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In this Wikipedia article re the Carbon Cub, an LSA with a 180 HP engine, somebody wrote "In order to maintain certification under American Light Sport Aircraft limitations the maximum takeoff power is limited to five minutes."

http://en.wikipedia.org/wiki/CubCrafters_Carbon_Cub_SS

If correct, what is the source and underlying reason for this 5 minute limitation? FAR 1.1's definition of "light sport aircraft" doesn't seem to contain it.

I ask because the POH for the Evektor SportStar I trained in also says that maximum takeoff power can only be applied for 5 minutes.

Thanks!
 
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register@teamandras.com said:
In this Wikipedia article re the Carbon Cub, an LSA with a 180 HP engine, somebody wrote "In order to maintain certification under American Light Sport Aircraft limitations the maximum takeoff power is limited to five minutes."

http://en.wikipedia.org/wiki/CubCrafters_Carbon_Cub_SS

If correct, what is the source and underlying reason for this 5 minute limitation? FAR 1.1's definition of "light sport aircraft" doesn't seem to contain it.

I ask because the POH for the Evektor SportStar I trained in also says that maximum takeoff power can only be applied for 5 minutes.

Thanks!
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The underlying reason in the Carbon Cub case is that the aircraft would be too fast for the LSA rules if the engine wasn't nudge-nudge-wink-wink "de-rated". The source is the POH which says the maximum take off power is limited to 5 minutes.


This is probably a different reason for the limitation than your SportStar. If it has a Rotax 912 / 914 it is limited to full power for 5 minutes as a basic limit on the engine straight from yea olde engine factory - I assume due to cooling.
 
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Capt. Geoffrey Thorpe said:
The underlying reason in the Carbon Cub case is that the aircraft would be too fast for the LSA rules if the engine wasn't nudge-nudge-wink-wink "de-rated". The source is the POH which says the maximum take off power is limited to 5 minutes.
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With regard to the Carbon Cub the issue is more one of weight. It would be tough to get a Cub airframe to cruise more than 120 knots no matter how much power you hang on it. Vno of a Carbon Cub is only 88 knots IAS anyway, and Vne is 122.

In addition to the 1320-lb MGW, the S-LSA rules prescribe a maximum empty weight. The formula is 1320 lb - (number of seats x 190) - (maximum continuous hp / 2).

My Sport Cub with a 100 hp O-200-A had a maximum empty weight of 890 lb (1320 minus 380 lb for two seats, minus half the max continuous horsepower). The Carbon Cub's engine is heavier, so by limiting max continuous horsepower to 80, it gave them ten more pounds of empty weight allowance to play with.
 
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Pilawt said:
With regard to the Carbon Cub the issue is more one of weight. It would be tough to get a Cub airframe to cruise more than 120 knots no matter how much power you hang on it. Vno of a Carbon Cub is only 88 knots IAS anyway, and Vne is 122.

In addition to the 1320-lb MGW, the S-LSA rules prescribe a maximum empty weight. The formula is 1320 lb - (number of seats x 190) - (maximum continuous hp / 2).

My Sport Cub with a 100 hp O-200-A had a maximum empty weight of 890 lb (1320 minus 380 lb for two seats, minus half the max continuous horsepower). The Carbon Cub's engine is heavier, so by limiting max continuous horsepower to 80, it gave them ten more pounds of empty weight allowance to play with.
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OK. But in either case, they are playing the system by plugging numbers into the POH.
 
That's not surprising, nor is it new. The old Cub, and aircraft like my Taylorcraft that have 65 hp engines are limited to 3 minutes at 2300 RPM before you can apparently do damage to the engine.

Ryan
 
Is there a specified number of minutes @ xxxx rpm for a Continental a-65 ? Does Continental specify that ? Many of the POH's or whatever they were called had no such limitation identified by the aircraft manafacutrer.

Dale
 
Capt. Geoffrey Thorpe said:
OK. But in either case, they are playing the system by plugging numbers into the POH.
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they aren't "playing" anything. They are complying with the rules via an acceptable method. Using a smaller engine with no POH restriction is another acceptable method.
 
Pilawt said:
In addition to the 1320-lb MGW, the S-LSA rules prescribe a maximum empty weight. The formula is 1320 lb - (number of seats x 190) - (maximum continuous hp / 2).
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Where do you find that formula? I didn't see it in the FARs, but maybe I haven't looked well enough.

As far as derating engines, many of us on here have flown engines that are derated for whatever reason. The engine on my T210 was 305 hp TO and 285 hp continuous, as I recall.
 
Lightning LS-1 with 120 hp Jabiru uses the same loophole. When they converted Esqual to LSA, they added 3 ft to wingspan, which slowed it down somewhat but not enough. So they have max continuous power for that reason.

Some engines have max continuous for honest reasons. My HKS has max continuous 60 hp at 6200 rpm for takeoff, but the manual requires it throttled to 5800 rpm no later than 5 minutes after takeoff, which gives about 56 hp. Obviously I'm not bumping against the legal speed limit for LSAs with that power :)
 
jnmeade said:
Where do you find that formula? I didn't see it in the FARs, but maybe I haven't looked well enough.
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Wouldn't be in the FARs, it'd be in the ASTM LSA standard. I seem to recall seeing it there, though I don't currently have access to my copy.

Ron Wanttaja
 
jnmeade said:
Where do you find that formula? I didn't see it in the FARs, but maybe I haven't looked well enough.
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It's in the ASTM standards for S-LSAs. See here.

Note that this formula only applies to aircraft certified under S-LSA standards. The new 100-hp American Champion 7EC Champ, on the other hand, is sport-pilot legal because its MGW is 1320 lb, fixed gear, fixed prop, has only two seats, cruises < 120 kts, etc. But it is a standard-category aircraft (same type certificate as the Citabria), not an S-LSA, so it can be sold with an empty weight of 925 pounds. That, of course, eats into the useful load.
 
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JHW said:
they aren't "playing" anything. They are complying with the rules via an acceptable method.
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Welllll... they're foisting the responsibility from the manufacturer (whose compliance can be verified) onto the operator (whose compliance cannot be). It's one thing when the limitation is due to a mechanical issue.

In the same fashion, I could install two extra seats, retractable gear, and a controllable-pitch prop on an LSA, as long as there's a placard that says "Do not use."

Ron Wanttaja
 
wanttaja said:
Welllll... they're foisting the responsibility from the manufacturer (whose compliance can be verified) onto the operator (whose compliance cannot be). It's one thing when the limitation is due to a mechanical issue.

In the same fashion, I could install two extra seats, retractable gear, and a controllable-pitch prop on an LSA, as long as there's a placard that says "Do not use."

Ron Wanttaja
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Um, I don't think so, unless you had something in mind like a LSA motorglider that was setup as an amphibian...

http://www.law.cornell.edu/cfr/text/14/1.1
Light-sport aircraft means an aircraft, other than a helicopter or powered-lift that, since its original certification, has continued to meet the following:
(1) A maximum takeoff weight of not more than—
(i) 1,320 pounds (600 kilograms) for aircraft not intended for operation on water; or
(ii) 1,430 pounds (650 kilograms) for an aircraft intended for operation on water.
(2) A maximum airspeed in level flight with maximum continuous power (VH) of not more than 120 knots CAS under standard atmospheric conditions at sea level.
(3) A maximum never-exceed speed (VNE) of not more than 120 knots CAS for a glider.
(4) A maximum stalling speed or minimum steady flight speed without the use of lift-enhancing devices (VS1) of not more than 45 knots CAS at the aircraft's maximum certificated takeoff weight and most critical center of gravity.
(5) A maximum seating capacity of no more than two persons, including the pilot.
(6) A single, reciprocating engine, if powered.
(7) A fixed or ground-adjustable propeller if a powered aircraft other than a powered glider.
(8) A fixed or feathering propeller system if a powered glider.
(9) A fixed-pitch, semi-rigid, teetering, two-blade rotor system, if a gyroplane.
(10) A nonpressurized cabin, if equipped with a cabin.
(11) Fixed landing gear, except for an aircraft intended for operation on water or a glider.
(12) Fixed or retractable landing gear, or a hull, for an aircraft intended for operation on water.
(13) Fixed or retractable landing gear for a glider.
 
RyanShort1 said:
Um, I don't think so, unless you had something in mind like a LSA motorglider that was setup as an amphibian...
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Not saying to try to do it to an existing, licensed airplane. But build from scratch and placard the features not permitted by the LSA definition. Isn't that exactly what the Carbon Cub is doing?

If the FAA complains, safety-wire the gear-retract switch and the prop-adjustment lever. The kind of wire they used to use on bread wrappers would do nicely. Kinda frail, though...might want to carry some extra, onboard.

Ron Wanttaja
 
wanttaja said:
Not saying to try to do it to an existing, licensed airplane. But build from scratch and placard the features not permitted by the LSA definition. Isn't that exactly what the Carbon Cub is doing?

If the FAA complains, safety-wire the gear-retract switch and the prop-adjustment lever. The kind of wire they used to use on bread wrappers would do nicely. Kinda frail, though...might want to carry some extra, onboard.

Ron Wanttaja
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no, not at all, retractable gear and constant speed props are expressly prohibited. There is no limitation on engine displacement or horsepower, no matter how much you seem to want there to be. If you could figure out a way to install a merlin and meet the weight it would be perfectly legal.
 
JHW said:
no, not at all, retractable gear and constant speed props are expressly prohibited. There is no limitation on engine displacement or horsepower, no matter how much you seem to want there to be. If you could figure out a way to install a merlin and meet the weight it would be perfectly legal.
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Nope, anything over 800hp requires a type rating.
 
Greg Bockelman said:
Reference?
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This is the only reference I found...

Vintage & Experimental Aircraft Program

This program standardizes pilot certification in the following U.S. aircraft:

Vintage Type Certificated aircraft which require a type rating
Experimental turbine-powered aircraft
Experimental aircraft with a maximum gross weight in excess of 12,500 pounds, or
Experimental piston powered aircraft with an engine over 800 HP and a Vne (never exceed speed) greater than 250 knots

http://www.faa.gov/licenses_certificates/vintage_experimental/
 
GauzeGuy said:
This is the only reference I found...

Vintage & Experimental Aircraft Program

This program standardizes pilot certification in the following U.S. aircraft:

Vintage Type Certificated aircraft which require a type rating
Experimental turbine-powered aircraft
Experimental aircraft with a maximum gross weight in excess of 12,500 pounds, or
Experimental piston powered aircraft with an engine over 800 HP and a Vne (never exceed speed) greater than 250 knots

http://www.faa.gov/licenses_certificates/vintage_experimental/
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wow that's convoluted reasoning. For starters, LSA's hardly go 250 kts. I feel like I'm listening to jeremy clarkson: "No, it's not the Ron, it's the Ron's beer-drinking EMT cousin"
 
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