Can you turn a constant speed prop into a fixed pitch?
Moderator: drseti
Re: Can you turn a constant speed prop into a fixed pitch?
I believe you're thinking about the Rotax 915iS, Ed. Like most turbocharged engines, it performs best driving a constant speed prop, and can be FADEC controlled (single lever). Certainly not intended for the LSA market, since the 915 is a very heavy engine.
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US
Re: Can you turn a constant speed prop into a fixed pitch?
There are 912is powered airplanes that are set up that way, but they are not LSA.
-
- Posts: 226
- Joined: Mon Apr 27, 2020 6:23 pm
Re: Can you turn a constant speed prop into a fixed pitch?
It's heavy but some manufacturers have made it work like the Bristell 915 with useful load to spare, even if it wasn't intended.drseti wrote:I believe you're thinking about the Rotax 915iS, Ed. Like most turbocharged engines, it performs best driving a constant speed prop, and can be FADEC controlled (single lever). Certainly not intended for the LSA market, since the 915 is a very heavy engine.
Re: Can you turn a constant speed prop into a fixed pitch?
Even John Rathmell, the marketing manager for Bristell USA, said in a recent AOPA Pilot interview about that aircraft, "It's too heavy."fatsportpilot wrote: the Bristell 915 with useful load to spare,
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US
-
- Posts: 226
- Joined: Mon Apr 27, 2020 6:23 pm
Re: Can you turn a constant speed prop into a fixed pitch?
The useful load is 500 lbs which is more than some LSAs with the 912ULS.drseti wrote:Even John Rathmell, the marketing manager for Bristell USA, said in a recent AOPA Pilot interview about that aircraft, "It's too heavy."fatsportpilot wrote: the Bristell 915 with useful load to spare,
Re: Can you turn a constant speed prop into a fixed pitch?
There are no miracles and they have to work with commonly known materials just as everyone else so the only explanations is that they are cutting corners somewhere ( for instance more fragile landing gear or some other parts ) and since the plane is relatively new and with relatively few of them out being there , we just don’t have enough data - it may very well be that their trade offs are actually reasonable and will not result in any serious issues ... who knows ...will see.fatsportpilot wrote:The useful load is 500 lbs which is more than some LSAs with the 912ULS.drseti wrote:Even John Rathmell, the marketing manager for Bristell USA, said in a recent AOPA Pilot interview about that aircraft, "It's too heavy."fatsportpilot wrote: the Bristell 915 with useful load to spare,
Flying Sting S4 ( N184WA ) out of Illinois
-
- Posts: 226
- Joined: Mon Apr 27, 2020 6:23 pm
Re: Can you turn a constant speed prop into a fixed pitch?
I think I read somewhere that they are using really thin aluminum and compensating by adding more flush rivets.Warmi wrote:There are no miracles and they have to work with commonly known materials just as everyone else so the only explanations is that they are cutting corners somewhere ( for instance more fragile landing gear or some other parts ) and since the plane is relatively new and with relatively few of them out being there , we just don’t have enough data - it may very well be that their trade offs are actually reasonable and will not result in any serious issues ... who knows ...will see.fatsportpilot wrote:The useful load is 500 lbs which is more than some LSAs with the 912ULS.drseti wrote:
Even John Rathmell, the marketing manager for Bristell USA, said in a recent AOPA Pilot interview about that aircraft, "It's too heavy."
Re: Can you turn a constant speed prop into a fixed pitch?
This aircraft is 115 pounds heavier than the 912-powered Bristell. That is a non-trivial difference, considering that the Bristell is noted for its excellent useful load. 70 pounds of that weight increase is just the engine. The other 45 pounds is the 4-bladed prop, plus what they put in to support that engine. This from AOPA Pilot, April 2020:
https://www.aopa.org/news-and-media/all ... istell-915
See the whole article at:"First of all, it’s too heavy,” said John Rathmell, national sales manager for Bristell Aircraft in Lititz, Pennsylvania, a U.S. dealer for the Bristell.
https://www.aopa.org/news-and-media/all ... istell-915
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US
-
- Posts: 226
- Joined: Mon Apr 27, 2020 6:23 pm
Re: Can you turn a constant speed prop into a fixed pitch?
Ok I see. I thought "too heavy" you meant too heavy to be legal. The useful load goes way down but it could still fit a rather large pilot and a child or maybe two small pilots. There are some LSAs with 300 or 400 lbs useful load which is incredibly low.
Re: Can you turn a constant speed prop into a fixed pitch?
There are ASTM rules that set minimum useful load requirements. For 2-place SLSA, I seem to recall the minimum useful load requirement is something like two 180 pound occupants, and enough fuel for 1 hour of flight at normal cruise power, plus a 30 minute day VFR reserve. For a Rotax 912 powered aircraft that burns 5 GPH, that required useful load comes to (2 x 180#) + (6#/gal x 7.5 gal) = 405 pounds. So, only a 1-place LSA could get away with a lower useful load.fatsportpilot wrote: There are some LSAs with 300 or 400 lbs useful load which is incredibly low.
SEE CORRECTIONS BELOW
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US
Re: Can you turn a constant speed prop into a fixed pitch?
Actually, I was mistaken about the details of the ASTM useful load rule. It's a little worse than I thought - this from Dan Johnson:
(Nof that I'm in any danger of buying one, at $296k!)
So by that formula,, the Bristsll 915 (which has an engine that can produce 141 HP) must have a useful load of at least 450.5 pounds, and a max empty weight of 869.5 pounds. The Bristell 915 reviewed in AOPA Pilot meets that spec - but if you want to order one with any additional options, you may be out of luck.Currently that requirement is 430 pounds for fixedwing airplanes (land). That number was arrived at by allowing 190 pounds for each seat occupant (380 pounds for two-seat S-LSA), and one-half the horsepower in pounds (for example: with a 100-hp engine add 50 pounds).
Accordingly, any fixed-wing S-LSA that has an empty weight of more than 890 pounds (with all options added) is being manufactured and operated in violation of the ASTM standard. Buyers of S-LSA are advised to determine whether an S-LSA meets this standard before purchasing or operating it. Bottom line: Don’t buy a new S-LSA that has an empty weight greater than 890 pounds.
(Nof that I'm in any danger of buying one, at $296k!)
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US
Re: Can you turn a constant speed prop into a fixed pitch?
It's not quite that bad , you actually would have 3 more pounds of useful load. The formula is based on maximum continuous power, so you would use 135 horsepower. This is the reason that the Carbon Cub has a maximum continuous power of 85 horsepower, not speed as everyone seems to think.drseti wrote:Actually, I was mistaken about the details of the ASTM useful load rule. It's a little worse than I thought - this from Dan Johnson:
So by that formula,, the Bristsll 915 (which has an engine that can produce 141 HP) must have a useful load of at least 450.5 pounds, and a max empty weight of 869.5 pounds. The Bristell 915 reviewed in AOPA Pilot meets that spec - but if you want to order one with any additional options, you may be out of luck.Currently that requirement is 430 pounds for fixedwing airplanes (land). That number was arrived at by allowing 190 pounds for each seat occupant (380 pounds for two-seat S-LSA), and one-half the horsepower in pounds (for example: with a 100-hp engine add 50 pounds).
Accordingly, any fixed-wing S-LSA that has an empty weight of more than 890 pounds (with all options added) is being manufactured and operated in violation of the ASTM standard. Buyers of S-LSA are advised to determine whether an S-LSA meets this standard before purchasing or operating it. Bottom line: Don’t buy a new S-LSA that has an empty weight greater than 890 pounds.
(Nof that I'm in any danger of buying one, at $296k!)
Re: Can you turn a constant speed prop into a fixed pitch?
Wow, that makes all the difference in the world!3Dreaming wrote:It's not quite that bad , you actually would have 3 more pounds of useful load.
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
facebook.com/SportFlying
SportPilotExaminer.US
Re: Can you turn a constant speed prop into a fixed pitch?
A half gallon of fuel.drseti wrote:Wow, that makes all the difference in the world!3Dreaming wrote:It's not quite that bad , you actually would have 3 more pounds of useful load.
- foresterpoole
- Posts: 307
- Joined: Thu Sep 22, 2016 12:28 pm
- Location: Alexandria, LA
Re: Can you turn a constant speed prop into a fixed pitch?
3Dreaming wrote:It's not quite that bad , you actually would have 3 more pounds of useful load. The formula is based on maximum continuous power, so you would use 135 horsepower. This is the reason that the Carbon Cub has a maximum continuous power of 85 horsepower, not speed as everyone seems to think.drseti wrote:Actually, I was mistaken about the details of the ASTM useful load rule. It's a little worse than I thought - this from Dan Johnson:
So by that formula,, the Bristsll 915 (which has an engine that can produce 141 HP) must have a useful load of at least 450.5 pounds, and a max empty weight of 869.5 pounds. The Bristell 915 reviewed in AOPA Pilot meets that spec - but if you want to order one with any additional options, you may be out of luck.Currently that requirement is 430 pounds for fixedwing airplanes (land). That number was arrived at by allowing 190 pounds for each seat occupant (380 pounds for two-seat S-LSA), and one-half the horsepower in pounds (for example: with a 100-hp engine add 50 pounds).
Accordingly, any fixed-wing S-LSA that has an empty weight of more than 890 pounds (with all options added) is being manufactured and operated in violation of the ASTM standard. Buyers of S-LSA are advised to determine whether an S-LSA meets this standard before purchasing or operating it. Bottom line: Don’t buy a new S-LSA that has an empty weight greater than 890 pounds.
(Nof that I'm in any danger of buying one, at $296k!)
Irregardless, I'd say it's pushing usable at those weights, I mean you basically have no range or no passenger weight. Thanks for the correction on the engine, it appears I confused the engine model. This is all academic anyway, it's still not legal under the current standards. Possibly in the future we will see a re-write more in line with European ultralight standards which allow retractable gear and constant speed props. I'm not holding my breath considering any federal regulation changes seem to move at the speed of an out of breath snail....
Ed