Chip is making progress with the Merlin Lite

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BTCrenshaw

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The AC says a series of full power 1000 feet runs in item 20. And other alternate options.
55 knots is 63 miles per hour or 92 feet per second. So 1000 feet is 11 seconds.
Don't forget, a pilot of 170Lbs. I take that to mean no adjustment just because the pilot weighs more!
 

REVAN

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Empty weight and power-off stall speed are usually the most challenging criteria. Many typical ultralights will need over 70 HP to fail the maximum speed limit via the calculated method. Few designs can have that much power installed and still meet the weight restrictions. However, when you get to very clean designs like the Merlin, a smaller engine and/or a climb pitched propeller are usually how the max speed is restrained. Although, there is nothing in AC-103 that would restrict the use of more innovative solutions.

Example: Use a throttle by wire system with airspeed and climb rate feeding into the throttle position controller. Then you can have a more powerful engine with acceptable climb performance while conditionally limiting the power to retard the maximum speed to legal limits when you are flying straight and level. If you are climbing, or descending the speed is not restricted in AC-103. Climb at 75 mph, then descend at 100 mph; repeat until you reach your destination. However, if you take on a level cruise, it automatically throttles back to 63 mph even if the power lever is advanced to the stop.

Since electric propulsion works better with clean airframes that require little power to stay aloft, the system described above would be a good method to control the legal speed of the aircraft while not sacrificing climb performance and safety.
 
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Armilite

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Empty weight and power-off stall speed are usually the most challenging criteria. Many typical ultralights will need over 70 HP to fail the maximum speed limit via the calculated method. Few designs can have that much power installed and still meet the weight restrictions. However, when you get to very clean designs like the Merlin, a smaller engine and/or a climb pitched propeller are usually how the max speed is restrained. Although, there is nothing in AC-103 that would restrict the use of more innovative solutions.

Example: Use a throttle by wire system with airspeed and climb rate feeding into the throttle position controller. Then you can have a more powerful engine with acceptable climb performance while conditionally limiting the power to retard the maximum speed to legal limits when you are flying straight and level. If you are climbing, or descending the speed is not restricted in AC-103. Climb at 75 mph, then descend at 100 mph; repeat until you reach your destination. However, if you take on a level cruise, it automatically throttles back to 63 mph even if the power lever is advanced to the stop.

Since electric propulsion works better with clean airframes that require little power to stay aloft, the system described above would be a good method to control the legal speed of the aircraft while not sacrificing climb performance and safety.
==================

My T-Bird I with a 447UL (40hp) Cruise Speed is 60mph! With a 503UL (50hp) Crusie is 65mph. A T-Bird I with a 277UL makes the 254lbs and is 65lbs complete. A Simonini Victor 1 Super is 70 lbs and 54hp. Could I cut 5 lbs off the Airframe to make it Work, Yes!

T-Bird I Spec.jpg
 

TWilkie

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Empty weight and power-off stall speed are usually the most challenging criteria. Many typical ultralights will need over 70 HP to fail the maximum speed limit via the calculated method. Few designs can have that much power installed and still meet the weight restrictions. However, when you get to very clean designs like the Merlin, a smaller engine and/or a climb pitched propeller are usually how the max speed is restrained. Although, there is nothing in AC-103 that would restrict the use of more innovative solutions.

Example: Use a throttle by wire system with airspeed and climb rate feeding into the throttle position controller. Then you can have a more powerful engine with acceptable climb performance while conditionally limiting the power to retard the maximum speed to legal limits when you are flying straight and level. If you are climbing, or descending the speed is not restricted in AC-103. Climb at 75 mph, then descend at 100 mph; repeat until you reach your destination. However, if you take on a level cruise, it automatically throttles back to 63 mph even if the power lever is advanced to the stop.

Since electric propulsion works better with clean airframes that require little power to stay aloft, the system described above would be a good method to control the legal speed of the aircraft while not sacrificing climb performance and safety.
Interesting approach! For sure it would be easier to employ this idea for an electric UL which will have an electronic controller. Seems complicated for a gas engine which typically has mechanical linkage.

Looking back, I'm not sure I captured the essence of my original thought. It appears that full power means full throttle in terms of part 103; I don't know how else to interpret AC 103-7. Sticking with mechanical linkage for the Merlin Lite, a streamlined plane, it seems like you have two choices:
1. Engine/prop combination with a throttle stop at max continuous RPM such that you get 55 knots in level flight. But you would sacrifice some climb ability by never going WOT.
2. Engine/prop combination with a throttle stop at max WOT engine RPM (short duration) such that you get 55 knots in level flight. This would give you better climb, but you would sacrifice cruise speed as you would need to reduce the RPM after a minute or two or three depending on the engine.
Seems like a compromise either way, but that is airplane design I guess.

The Merlin lite will not meet the AC 103-7 appendix charts for maximum speed or stall so will require a "Recognized Technical Standards Committee" evaluation to be a true ultralight and be legal under 103 rules.
 

n3puppy

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==================
My T-Bird I with a 447UL (40hp) Cruise Speed is 60mph! With a 503UL (50hp) Crusie is 65mph. A T-Bird I with a 277UL makes the 254lbs and is 65lbs complete. A Simonini Victor 1 Super is 70 lbs and 54hp. Could I cut 5 lbs off the Airframe to make it Work, Yes!
What is the calculated MAX speed of your T-bird with a Simonini 54hp motor since it already busts 63mph at cruise with a 50hp engine? (447 probably busts too if 60mph at cruise)

No sense trimming 5lbs to make legal weight if pushs past max level flight speed of 55 knots.
 

galapoola

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Yes, it's better to be lighter than the arbitrary 254 pound limit. It's just hard to do and have extras like an enclosed cockpit. It's not easy to just have a seat.
James Wiebe from the defunct Belite had demonstrated some ultralite designs w/o the turtledeck cover, seat cushions and possibly doors. I believe he said for a ramp check weight those come off so you are under and then you add them back in if you so choose to fly since they are not necessary or permantly part of the aircraft.
 

Armilite

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What is the calculated MAX speed of your T-bird with a Simonini 54hp motor since it already busts 63mph at cruise with a 50hp engine? (447 probably busts too if 60mph at cruise)

No sense trimming 5lbs to make legal weight if pushs past max level flight speed of 55 knots.
=====================

My Point was, he said an Ultralight probably needed 70hp to bust the Max Full Power Speed of 55 knots. I just showed him they don't! Most Ultralights with probably just 35hp and the right Prop & Reduction can get real close to 55 knots.

Single Cylinder Engines like the Heaviest that you can make Part 103 at the Rotax 277UL at 65 lbs, Compact Radial MZ34 at 42 lbs, Simonini Mini 3 at 44 lbs, Polini 250 at 45 lbs, Hirth F33 at 45 lbs, can all be upgraded to make 35+hp! The Simonini Victor 1 Series is only 70 lbs, 5 lbs more than the Rotax 277UL, and comes in 44hp, 48hp, 54hp. The Aerolite 103 with a Hirth F33 is 235 lbs - 45 lbs = 190 lbs for Airframe + 70 lbs = 260 lbs, so 6 lbs over. Would using a BRS Exemption make it Work, Yes! Airframe at 190 lbs + 65lbs (277F) = 255 lbs! Only 1 pound over for the Aerolite 103.
 

n3puppy

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=====================
My Point was, he said an Ultralight probably needed 70hp to bust the Max Full Power Speed of 55 knots. I just showed him they don't! Most Ultralights with probably just 35hp and the right Prop & Reduction can get real close to 55 knots.
Would using a BRS Exemption make it Work, Yes!
My point was - YOU didn't get his point.
He was talking about staying Part 103 ultralight legal by using the FAA AC103-7 calculation for top speed.
NOT actual speed. Using the FAA calc it is hard to bust 55knots with under 70hp.

Show up with an undocumented T-bird with a non stock engine combo and you need something to show the FAA that you have:
Satisfactory Evidence The use of the graphs provided in Appendixes 1 and 2 will be acceptable for determination of the maximum level flight speed and power-off stall speed if your ultralight has no special limitations to maximum speed or power and no special high-lift-devices.

Your advertising information tells the FAA a T-Bird will CRUISE at 60MPH with only 40 hp. So now that you told them - any of your single engine options over the ORIGINAL 28hp 277UL is asking for a ramp-check.

BTW - you also don't have the BRS exemption right - FAA doesn't give extra lbs for the airframe.
 

Armilite

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My point was - YOU didn't get his point.
He was talking about staying Part 103 ultralight legal by using the FAA AC103-7 calculation for top speed.
NOT actual speed. Using the FAA calc it is hard to bust 55knots with under 70hp.

Show up with an undocumented T-bird with a non stock engine combo and you need something to show the FAA that you have:
Satisfactory Evidence The use of the graphs provided in Appendixes 1 and 2 will be acceptable for determination of the maximum level flight speed and power-off stall speed if your ultralight has no special limitations to maximum speed or power and no special high-lift-devices.

Your advertising information tells the FAA a T-Bird will CRUISE at 60MPH with only 40 hp. So now that you told them - any of your single engine options over the ORIGINAL 28hp 277UL is asking for a ramp-check.

BTW - you also don't have the BRS exemption right - FAA doesn't give extra lbs for the airframe.
======================

He didn't give an example, he just made the statement. I find it very hard to believe the FAA Speed Formula would be that far off. Back then when they made up part 103 Rules most Part 103 Airframes could only make the 254 lbs Empty Weight with a Rotax 277UL, that's WHY 85% used the 277UL. None of these other Engine Companies were around back then making Light Weight Singles like we have today. My T-Bird I is one of the Oldest made and with a Rotax 277UL just made Weight. The FAA accepts the Manufactures Engine Specs follow the Part 103 Rules! They don't Check Weights unless grossly out of Specs! They don't Check Full Power Speeds either. All they really care about is that you're using just 5 Gallons.

55 knots - 63.29287 mph

If Cruise is 60mph it was on less than the 447UL 40hp! Like I said, probably 35hp. Even a 277UL could be upgraded to make that hp. You can't tell the difference between a 26hp 277 and 28hp 277

268.8cc/[email protected]= 10.3cc to make 1hp with Rotax's Header Muffler!

268.8cc/[email protected] = 9.6cc to make 1hp with Rotax's Header Muffler!
==========================================

A 277UL Big Bored (82mm x 66mm) 348.6cc!

348.6cc/10.3cc = [email protected] with a Muffler!

348.6cc/9.6cc = [email protected] with a Muffler!

The FAA doesn't know what hp your Engine is making! They might Look at a Tuned Pipe, but more out of curiosity than anything. I don't know of anybody who has ever been Ramped Checked by any FAA. I have talked to some at Oshkosh who told me they're mainly interested in compliance with the 5 Gallon Rule.

The BRS Exemption gives you I believe 28 lbs, which Part 103 at 254 lbs + 28 lbs = 282 lbs! So as long as your under 282 lbs total your Good! They don't make you take off the BRS and Weight the Airframe.

That's how Chips New Merlin Lite Ultralight with the Expensive Polini 36hp 54-55 lbs makes Part 103 is with the BRS Exemption. It's like only 3-4 lbs overweight, so needs a $4000+ BRS Exemption with that Engine! Even though it will make Part 103 Weight with the Hirth F33 (28hp), and with the MZ34 (30hp), and with the Simonini Mini 3 (32hp). Probably could even make Weight with a Rotax 277UL Free Air with a Belt Drive if put on a Diet. When I talked to him the MTOW was at 500 lbs but said most likely will be 550 lbs after structural tests are completed. With the right Engine, I think it will Sell really well. But not with a Polini.

500 lbs = 226.7962 kg / 10 kg = 22.67962 kw needed = 30.41387 hp needed!

550 lbs = 249.4758 kg / 10 kg = 24.94758 kw needed = 33.45526 hp needed!

That's also How the Aerolite 103 makes Part 103 weight with the Hirth F23 (50hp)! I'm sure the 50hp is also pushing it over 55 knots also.

You don't have to Document a Part 103! It's not Classified as an Airplane!
 

n3puppy

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The FAA accepts the Manufactures Engine Specs follow the Part 103 Rules! They don't Check Weights unless grossly out of Specs! They don't Check Full Power Speeds either. All they really care about is that you're using just 5 Gallons.

The BRS Exemption gives you I believe 28 lbs, which Part 103 at 254 lbs + 28 lbs = 282 lbs! So as long as your under 282 lbs total your Good!

You don't have to Document a Part 103! It's not Classified as an Airplane!
You should start a 103 thread because much of what you said is not per Part 103
No need to hijack this thread discussing it with you.

In the meantime read the advisory circular listed a few posts ago
https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_103-7.pdf
Documentation required Para. 24
Only check fuel size Para 24(c-2)
Airspeed checks Para 24(b)
Safety device exemption Para 18(1-i)
FAA accepts Manufactures specs Para 11(a,b,c)
 
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REVAN

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My point was - YOU didn't get his point.
He was talking about staying Part 103 ultralight legal by using the FAA AC103-7 calculation for top speed.
NOT actual speed. Using the FAA calc it is hard to bust 55knots with under 70hp.
Exactly.

He didn't give an example, he just made the statement. I find it very hard to believe the FAA Speed Formula would be that far off.
I haven't analyzed many designs, but I am working on my own design and I have analyzed that. It is pretty low profile and small compared to many other designs, but it does use standard ultralight aluminum tube construction with strut and wire bracing. When I ran the FAA calculation on my design, I came up with a little over 70 Hp as the limit for my airframe. I was surprised it was that high, about double what I'm intending to use. Conclusion: I don't need to worry about the max speed with my design. My focus will be on complying with the empty weight and power off stall speed requirements.

With my design looking like a more compact and efficient layout than a Quicksilver or similar ultralight, I was generalizing that the formula would likely produce similar results on other designs of similar construction. The formula looks at wing and tail size, pilot exposure, engine exposure, landing gear, and the exposed linear feet of struts and wires. I have a big wing and tail and I don't have a pilot enclosure, engine cowl, or wheel pants, so those features will increase the calculated drag for my design.
 

REVAN

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==================

My T-Bird I with a 447UL (40hp) Cruise Speed is 60mph! With a 503UL (50hp) Crusie is 65mph. A T-Bird I with a 277UL makes the 254lbs and is 65lbs complete. A Simonini Victor 1 Super is 70 lbs and 54hp. Could I cut 5 lbs off the Airframe to make it Work, Yes!

View attachment 108133
I'm noticing that the T-Bird 1 is not an ultralight with any of these Rotax engine options. Even if these listed weights include a BRS (though that is not indicated), even the 447 powered T-Bird is listed over 278 pounds pounds empty (the limit with a BRS inclusive). The listed aircraft shown above don't need to meet any 103 restrictions, but they will need an N-number.
 

Armilite

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I'm noticing that the T-Bird 1 is not an ultralight with any of these Rotax engine options. Even if these listed weights include a BRS (though that is not indicated), even the 447 powered T-Bird is listed over 278 pounds pounds empty (the limit with a BRS inclusive). The listed aircraft shown above don't need to meet any 103 restrictions, but they will need an N-number.
=========================

Your Correct the T-Bird 1 doesn't make Part 103 Weight with a 447UL, or the 377UL which was 2 pounds lighter. It only makes USA Part 103 Weight with the Rotax 277UL (28hp) and which weighs 65 lbs. But it makes Weight today with the Hirth F33 at 45 lbs, the MZ34 at 43 lbs, the Simonin Mini 3 at 42 lbs, the Polini 250 DS at 55 lbs. Most of these Newer Engines are larger CC and with a Tuned Pipe can make more than 40hp which we were Showing, 40hp would Push it over the Part 103 Max Full Power Speed of 55 knots. A 277UL with a Good Tuned Pipe could make [email protected]

55 knots = 63.29287 mph

A 277UL turned 6500rpm making 38hp with a Tuned Pipe with a 2.0 Redrive 3250rpm, Pitched for 3150rpm with a 56" x 21 Prop, makes 222.39 lbs of Static Thrust and needs 37.276 hp and approximate Max Speed is 62.6 mph.

277UL 38hp - 2..jpg277UL 38hp - 1..jpg
 
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Armilite

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A 277UL turned 6500rpm making 33hp with a Tuned Pipe with a 2.0 Redrive 3250rpm, Pitched for 3150rpm A 54" x 21 Prop, makes 192.28 lbs of Static Thrust and needs 32.229 hp and approximate Max Speed is 62.6 mph.

277UL was rated [email protected], probably [email protected] with a better Muffler. With just some Cylinder and Case Porting you can Gain 15%. 29hp + 15% = 33.35hp!
277UL 33hp - 2..jpg277UL 33hp - 1..jpg
 

REVAN

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@Armilite,

It looks like the T-Birds have several different options for pilot enclosure. Looking at online pictures, I see no enclosure, partial enclosure and full enclosure options shown. What version are you referencing?

It would be helpful for everyone here if you were to calculate the max power allowed for the T-Bird according to Appendix 1 of FAR 103-7. Would you be willing to do that and post your results here?

Maybe post it here as well: Part 103 Max Speed vs. Climb Power

Regarding the screenshot tables above, the "Estimated flying speed" shown in those tables is no indication of how fast your aircraft will be with that power and propeller. That speed is just the propeller pitch multiplied by the propeller RPM and converted to MPH. It is basically a no-slip propeller calculation. Any aircraft with drag will not achieve that, and ultralights usually have quite a bit of drag when you try to push them fast through the air.
 

Armilite

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@Armilite,

It looks like the T-Birds have several different options for pilot enclosure. Looking at online pictures, I see no enclosure, partial enclosure and full enclosure options shown. What version are you referencing?

It would be helpful for everyone here if you were to calculate the max power allowed for the T-Bird according to Appendix 1 of FAR 103-7. Would you be willing to do that and post your results here?

Maybe post it here as well: Part 103 Max Speed vs. Climb Power

Regarding the screenshot tables above, the "Estimated flying speed" shown in those tables is no indication of how fast your aircraft will be with that power and propeller. That speed is just the propeller pitch multiplied by the propeller RPM and converted to MPH. It is basically a no-slip propeller calculation. Any aircraft with drag will not achieve that, and ultralights usually have quite a bit of drag when you try to push them fast through the air.
=====================

I don't really care about the Numbers, it qualified for Part 103 with the Rotax 277UL at the time. To the FFA it Looks like a Rotax 277UL, Sounds like a 277UL, the FAA doesn't need to know if it's still making 28hp or 32hp, or 35hp, or 38hp.

Only Info I have found with a T-Bird I and the 277UL 28hp.

Most have Full Cabin. In the Summer most take off the Doors for better Cooling for the Pilot.

By Indy Aircraft the Manufactures Numbers we know it Cruises at 60mph with a 447UL rated (40hp) for takeoff, so Crusie hp would be less than 40hp. 40hp at 75% Power equals 30hp. So probably between 30-35hp.

If you noticed, one almost made 62.6mph with 32hp.

For the Prop (CF) in the Prop Thrust Calc, I used, .85! it could be less or higher than that. No matter what, you want to match the Prop Size & Pitch for the Engines Max [email protected]

38hp is the Max the 277UL could make at 6500rpm with a Good Tuned Pipe with mild Porting and proper Size Carb, which I believe a 38mm is the Largest it can use without Machining.

All these can make Part 103 Engines using 6500rpm:

Rotax 277UL(28hp) = 268cc/7cc= [email protected]!

Hirth F33(28hp) = 313cc/7cc = 44.7hp!

Compact Radial MZ34(30hp) = 313cc/7cc = 44.7hp!

Simonini Mini 3(30hp) = 270cc/7cc = 38.5hp!

Polini Thor 250cc/7cc(28-30hp) = 35.7hp!

T-Bird I Spec.jpgTERRIA I - T-BIRD I with 277UL.jpg
 

n3puppy

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@Armilite,
It would be helpful for everyone here if you were to calculate the max power allowed for the T-Bird according to Appendix 1 of FAR 103-7. Would you be willing to do that and post your results here?

Maybe post it here as well: Part 103 Max Speed vs. Climb Power
Revan- did some T-Bird calculating and posted it over on the thread you suggested.
 

REVAN

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I haven't analyzed many designs, but I am working on my own design and I have analyzed that. It is pretty low profile and small compared to many other designs, but it does use standard ultralight aluminum tube construction with strut and wire bracing. When I ran the FAA calculation on my design, I came up with a little over 70 Hp as the limit for my airframe. I was surprised it was that high, about double what I'm intending to use. Conclusion: I don't need to worry about the max speed with my design. My focus will be on complying with the empty weight and power off stall speed requirements.

With my design looking like a more compact and efficient layout than a Quicksilver or similar ultralight, I was generalizing that the formula would likely produce similar results on other designs of similar construction. The formula looks at wing and tail size, pilot exposure, engine exposure, landing gear, and the exposed linear feet of struts and wires. I have a big wing and tail and I don't have a pilot enclosure, engine cowl, or wheel pants, so those features will increase the calculated drag for my design.
OK... I see that I made a significant error when I did the Appendix 1 max speed calculation for my design. In hindsight, I glossed over this part because I was not worried about it. My design is slow (foot launch slow), and I knew that I was not going to be pressing any upper speed limits. I wanted to do the Appendix 2 power-off stall speed calculation, but the max speed calculation in Appendix 1 comes first in the document. I almost skipped over the first part entirely, but decided to do a quick evaluation and move on. This is how I ended up doing it wrong.

Calculating drag on struts and wires involves taking a 2-D drag coefficient and multiplying that by a reference area and a dynamic pressure. That area is usually made up of the diameter or thickness and the length of the element being analyzed. This led me to falsely assume that the strut and wire coefficients get multiplied by the length of the element being included in the appendix 1 calculation. This is not how the table works. The calculation assumes an average diameter and length for any included wire or strut. The table instructs to simply multiple the given coefficient by the number of struts, not by the lengths of the struts (and same with wires). In effect, I was giving a 7 foot wing strut an erroneously allocated 7 times drag allocation. It's a big error, I know. But it was not big enough to take it off the chart, probably because I have a fairly small and compact design to begin with.

Redoing the calculation, it looks like my design is likely going to be operating in the 11 to 12 curve range on the Speed vs. Power reference plot in Appendix 1. My design will be limited to the 35 to 38 Hp range unless I can show compliance through flight test.
 
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