Real World Astore Performance

[danal]

I recently flew Astore N837TA (Rotax 914) from Mankato Minnesota to 5TX0 (Hidden Valley) in North Texas.  Weather caused some interesting routing, and a full day's delay at one point.  I've taken the log data from the Garmin G3X system, subset it to entries where airspeed was over 40 (i.e. flying), done some other filtering, and produced a composite "RPM v TAS" graph. 

Caveats: Total flight time was about 8 hours.  Should have been closer to 6 or 7 depending on headwinds... weather routing explains the increase.  Quite a bit of the flight was MVFR at 2500 MSL feet or below.  A couple of hours were at 5500 and one hour was at 6500.  I would expect the TAS numbers to be a little higher if more of the flight was at 10,000, etc. 

So, anyway, some real world numbers from a long cross country that was forced low due to weather.  Routing:


Duration Start End Comment
1:27:14 KMKT KMDS Almost due west to get out of weather (direct route would be almost due south)


2:58:50 KMDS KCNK Reached Concordia Kansas just before sunset.  Ended up here for two nights (one day) as a weather hold.


2:09:42 KCNK KOJA KOJA is Weatherford OK, home of Tomas P. Stafford, the Apollo astronaut. There is a GREAT museum on the field.  Held here for about 3 hours waiting on weather.


1:30:26 KOJA 5TX0 HOME!!! Pretty darn MVFR for the last 45 min.


• Yellow band on RPM indicates permissible power for 5 minutes at takeoff. Continuous power must be below 5500. 
• TAS is in knots. 
• Title says "Mostly 5500 feet".  Probably more like "Mostly really low, some 5500 feet"

[montanapilot]

I went up a couple of days ago to check actual fuel burn. I climbed to (nice coincidence) 5,500'. I then switched to a full tank, flew for an hour, and then switched back to the original tank. At 5450 rpm, TAS was 132 kts. and fuel burn was 7.8 gallons for that hour. I'm going to check other rpm settings, but I'd guess that at 5400 rpm I'll do around 125 kts and 7 gph or a bit less. Regardless, we're both getting relatively similar results.

[mackattack]

Thanks for posting guys ... Danal’s data is much more scientific a review than I ever did but my experience in 837TA is consistent with MontanaPilot’s. I also used a DUC prop for awhile which I think was able to add 2-3 knots over the Sensenich. Finally, my Astore had the Aviana ceramic coating treatment ... I think that may add a knot or two when all is said and done. You notice it most the closer you get to 10,000’ of course ...

[danal]

Apr 8, 2019 21:48:41 GMT montanapilot said:

I went up a couple of days ago to check actual fuel burn. I climbed to (nice coincidence) 5,500'. I then switched to a full tank, flew for an hour, and then switched back to the original tank. At 5450 rpm, TAS was 132 kts. and fuel burn was 7.8 gallons for that hour. I'm going to check other rpm settings, but I'd guess that at 5400 rpm I'll do around 125 kts and 7 gph or a bit less. Regardless, we're both getting relatively similar results.

Very similar.  I'll publish some more complete fuel numbers soon... meanwhile, they are going to be in the 6.6 to 6.8 GPH area. 

I believe my prop is currently set with Gauge#5 (I have not personally verified this). 

[sobpilot]

I'm not sure what my prop is set at, however my best cruise speed seems to be 5000-6000 ft at about 127kts TAS. The last few flights have been really bumpy so it's hard to hold RPM, but the average is around 5400 and I'm seeing about 6.5 GPH at this setting.

At 9000 ft and 5400-5500 RMP the best manifold pressure I can get is 29 in. Since I have converted the Astore to Experimental and flying it under my Private Pilot's privileges, I have an Airmaster Electric Constant Speed Prop on order. I hope to have it by the end of April and I'll report back on performance numbers. I expect to see around 135 kts TAS at higher altitudes with >32 in.

I also have the 914 and so far it has really been a great engine. Easy to start and very smooth running.

[mudlupilot]

Apr 10, 2019 14:10:11 GMT sobpilot said:

I'm not sure what my prop is set at, however my best cruise speed seems to be 5000-6000 ft at about 127kts TAS. The last few flights have been really bumpy so it's hard to hold RPM, but the average is around 5400 and I'm seeing about 6.5 GPH at this setting.

At 9000 ft and 5400-5500 RMP the best manifold pressure I can get is 29 in. Since I have converted the Astore to Experimental and flying it under my Private Pilot's privileges, I have an Airmaster Electric Constant Speed Prop on order. I hope to have it by the end of April and I'll report back on performance numbers. I expect to see around 135 kts TAS at higher altitudes with >32 in.

I also have the 914 and so far it has really been a great engine. Easy to start and very smooth running.

A constant speed prop is not authorized for LSA or E-LSA planes, it would need an experimental demonstration designation to add a constant speed prop and there would be severe restrictions flying it. Check with an aviation attorney.

[danal]

Apr 15, 2019 11:37:16 GMT mudlupilot said:

Apr 10, 2019 14:10:11 GMT sobpilot said:

A constant speed prop is not authorized for LSA or E-LSA planes, it would need an experimental demonstration designation to add a constant speed prop and there would be severe restrictions flying it. Check with an aviation attorney.

Unfortunately, in the US, this is correct. 

People are often confused by way a PILOT exercises privileges of "Private Pilot acting as Sport" vs. "How the Airworthiness Certificate was issued for the aircraft".  

Sport pilots, and/or Private acting as Sport, can fly anything that meets the definition of an LSA (1320, 120 at sea level, two seats...), no matter what Airworthiness certificate was originally issued to the aircraft itself.   Type Certified, Experimental Amateur (homebuilt), S-LSA, E-LSA, and more... as long as all LSA definitions are met, a pilot can fly it operating withing the privileges and restrictions of a Sport Pilot. 

That is entirely separate from how an Airworthiness certificate is issued to a particular aircraft.  It is true that an S-LSA, which is how the Astore is originally issued an AW cert when sold in the USA, it is true that the S can be converted to an E-SLA.  Long topic here and I'm going to skip most of it, and just say "S can go E at the drop of a hat, E can not (pragmatically) go back to S".  Again, long topic and not really the focus here; let's just assume a given Astore has been declared to be an "E"-LSA. 

Back to the prop: The resulting E-LSA is still a "Light Sport" aircraft and MUST continue to meet the definition of an LSA found in 14 CFR 1.1.  1320lbs, 120 kts at sea level, no more than two seats, and all the FARs about the prop, which boil down to "Ground adjustable, except gliders can have feathering props".  And no, the Astore can't be 'declared' a 'glider'.  The FARs do define legally what is/isn't a glider, based on aspect ratio, and the Astore is nowhere close.  And... "feathering", not "pitch adjustable". And... And... 

In short, an in-flight adjustable prop takes the aircraft out of the LSA definition, thus invalidating its airworthiness certificate. In fact, it might do it twice: Once by being adjustable and once by pushing cruise (at max power, sea level) above 120. 

I know of no way to re-certify it in another category, except MAYBE "Experimental Exhibition" or "Experimental R&D", both of which would require an incredibly flexible FSDO and both of which carry lots of restrictions of their own. 

So, yeah, bummer.  No legal way to put in-flight adjustable prop on an Astore in the US.  

[ash31mi]

Going to Experimental Exhibition is an interesting move in order to use the constant speed prop; finding a friendly and interested DAR to handle the re-certification is the hardest part but glider pilots are quite used to that when importing new sailplanes that don't have a U.S. type certificate. Flight test plan, typically 5 or 10 hours, and a logbook signoff, then an annual program letter. If the performance improvements are significant, offering a certified version of the Astore with this prop might be an interesting marketing option for Tecnam.

[Glenn]

Danal,

Good explanation but after reading your post, I'm curious how this Tecnam P2008 managed to go from S-LSA to Experimental Kit Built Airworthiness?
Maybe just a friendly DAR or FSDO...

[montanapilot]

The Experimental Exhibition category is a pain in the neck. I owned one several years ago (only category in which that type of plane could be certified), and for starters, every year you have to file a report with the FAA that shows every trip you intend to make that year, including the routing. In other words, no last-minute burger runs or weekend getaways. If you do want to do that, you have to notify your local FSDO by fax or e-mail first. Can you get away with it? It's one of those low-probability/high-risk decisions. If you have an incident or accident during a flight for which the FAA was not notified, you will have major problems, not only with the FAA but also with your insurance company.

[ash31mi]

Apr 15, 2019 14:48:04 GMT montanapilot said:

The Experimental Exhibition category is a pain in the neck. ..

Yes, but it doesn't have to be so draconian. 3 of the sailplanes I've owned were Experimental Exhibition, which is very common for imported sailplanes, and the DAR in each instance gave blanket permission to fly within a 300 mile radius of the home airport without the need to send in advance notice of individual flights. It comes down to finding a friendly DAR: a few years ago our local FSDO had someone who started giving limitations like that but it proved unworkable and the next guy went back to normal. The annual program letter is typically prepared to cover any flight from a set of predefined airports, plus the option to attend any officially-sanctioned contest anywhere in the country.

[Flocker]

Apr 15, 2019 14:48:04 GMT montanapilot said:

The Experimental Exhibition category is a pain in the neck. I owned one several years ago (only category in which that type of plane could be certified), and for starters, every year you have to file a report with the FAA that shows every trip you intend to make that year, including the routing.

Really?  Wow! First I've heard of this!

[danal]

Apr 15, 2019 15:04:57 GMT ash31mi said:

Apr 15, 2019 14:48:04 GMT montanapilot said:

The Experimental Exhibition category is a pain in the neck. ..

Yes, but it doesn't have to be so draconian. 3 of the sailplanes I've owned were Experimental Exhibition, which is very common for imported sailplanes, and the DAR in each instance gave blanket permission to fly within a 300 mile radius of the home airport without the need to send in advance notice of individual flights. It comes down to finding a friendly DAR: a few years ago our local FSDO had someone who started giving limitations like that but it proved unworkable and the next guy went back to normal. The annual program letter is typically prepared to cover any flight from a set of predefined airports, plus the option to attend any officially-sanctioned contest anywhere in the country.

I've even heard of people sending a letter to the FSDO for their Ex/Ex once a year saying their operating area is the continental US.   Heard of it... but can't verify it for an absolute fact...

So, yeah, Ex/Ex would be the most likely way to possibly get an Astore "re-" certified.  Then you could do anything you want, including the props that are DESIGNED for the 914 with oil based constant speed governors. HOWEVER... the pilot could no longer operate as a "sport"... would have to be Private or above. 

[montanapilot]

Per my previous post, I've been looking for a power setting that will keep the fuel burn to 7 gph. Again, per my previous post, I tried a couple of different altitudes and rpm's. I finally got to 7 gph. Here are the numbers:

5,500’ 5430-5460 rpm 132-133 kts. 7.8 gph
7,500’ 5,400 rpm 129 kts. 7.5 gph
7,500’ 5,300 rpm 126kts 7.0 gph

[ash31mi]

I ran a 4 1/4 hour fuel burn test flight last week, approx 230 nautical miles downwind at 9,500ft MSL and 240 nm back at 10,500ft. rpm target was between 5,000 and 5,100 rpm; TAS varied but guessing about 110 kts. Total fuel burn was 19 gallons, i.e. under 5 gph. For a long trip I figure the extra time in the air permitted by lower fuel burn and lower TAS will easily outweigh the more frequent refuelling stops with a high fuel burn. Being out west with generally clear skies helps, of course, to fly at higher altitude; next time I'll step up a couple of thousand feet each way and use oxygen.