E-Turbo for an E-UL (a legal 100mph Part 103 UL is possible!)

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Grimace

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...so long as it only reaches that speed while climbing and gets the power chopped back when in dead-level flight).

This is referencing an ultralight glider. In a nutshell, any powered UL glider is an "ultralight" and gets lumped in with the 254lb folks). I spent some time rereading Part 103 looking for ideas and came up with this-

Let's assume I had a 40kw e-motor which was capable of blasting past the 55kt limit. So I set the controller to limit power to 25kw in order to stay under the *maintaining level flight* requirement of part 103. Assume this would not be override-able in flight.

But what if I also had a "turbo" button that would allow me access to full power, but only under the following circumstances: Either when AOA is over 5 degrees, or for 2 minutes after a weight-on-wheels switch opens,

This would make it impossible to maintain level flight above 55kts, but it would also allow you to climb like a mf'r and get off the ground in a shorter distance. The FAR does say that artificial means of controlling level speed are ok and it's not really a work-around if it's only allowing access to more power in climb situations.

Hypothetically, sure, I could have a level speed of 55 but be capable of 100kts at a 3° AOA with a 50fpm climb rate. but I'm not even talking about working around the system, I just want to maximize performance within the rules. What do you think?
 
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TFF

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The original PT 103 rules did not have a speed limit but had a horsepower limit instead. There were 100+ mph ULs that the FAA did not think was possible. They changed the rules. Get too smart, they will change the rules.
 

BBerson

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“Either when AOA is over 5 degrees, or for 2 minutes after a weight-on-wheels switch opens,”
The 5 or 10 degree switch might work in accordance with AC103-7. The 2 minutes switch would not since the pilot could push to level on takeoff and exceed the 55 knots.

(quote button not working today?)
 

Vigilant1

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- Is AoA the right parameter to use for your throttle limiting trigger? I don't think so. You could have a 5 degree AoA and have the nose pointed straight down, or on the horizon. Conversely, you could be ”in level flight" (and thus needing to limit airspeed to 55 Kts to meet the reg) at any AoA across a wide range. "Level flight" means zero vertical velocity, it has no fixed relationship to AoA, deck angle, etc. So, I think to meet the reg in this hairsplitting way, you'd need to do your throttle limiting only when VVI is zero and airspeed is above 55kts.

- There's nothing inherently "e" about this idea, right? The same "throttle limiting in level flight" could be achieved with an IC engine equipped with EFI.

- I don't think any throttle limiting (triggered by AoA, VVI, etc) would be a good idea from a safety standpoint. A key step in many stall recoveries is to apply power--maybe all of it. You might be in level flight at that time, and you might be at a modest AoA (as the nose drops).

- I don't think the idea will survive contact with the FAA. If they don't shoot you down with a local ruling/interpretation, then they'll just modify the words of the existing reg to meet their obvious intent: " no greater than 55 knots when in level flight or climbing."
 
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llemon

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I assumed this thread would be about assuming the speed limit is only applicable at sea level and using a turbo to get additional speed legally. A computer controlled waste gate could be used to make the turbo worthless at SL, and have a peak output greater than SL power at say 10k feet.
 

Grimace

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“Either when AOA is over 5 degrees, or for 2 minutes after a weight-on-wheels switch opens,”
The 5 or 10 degree switch might work in accordance with AC103-7. The 2 minutes switch would not since the pilot could push to level on takeoff and exceed the 55 knots.

(quote button not working today?)
But the pilot could also enter a dive, level off, and exceed 55kts in level flight. How is exiting a climb different from exiting a dive? Except for the way that breaks the laws of physics and "but, it's not supposed to work that way". Clearly, the requirement means it must be able to sustain that speed with power. And while it can achieve a higher speed the software prevents you from sustaining it. Also, the FAA stated that the 55kt restriction is not a speed limit (their words, not mine). So I think you might be ok there too.
 

Grimace

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- Is AoA the right parameter to use for your throttle limiting trigger? I don't think so. You could have a 5 degree AoA and have the nose pointed straight down, or on the horizon. Conversely, you could be ”in level flight" (and thus needing to limit airspeed to 55 Kts to meet the reg) at any AoA across a wide range. "Level flight" means zero vertical velocity, it has no fixed relationship to AoA, deck angle, etc. So, I think to meet the reg in this hairsplitting way, you'd need to do your throttle limiting only when VVI is zero and airspeed is above 55kts.

- There's nothing inherently "e" about this idea, right? The same "throttle limiting in level flight" could be achieved with an IC engine equipped with EFI.

- I don't think any throttle limiting (triggered by AoA, VVI, etc) would be a good idea from a safety standpoint. A key step in many stall recoveries is to apply power--maybe all of it. You might be in level flight at that time, and you might be at a modest AoA (as the nose drops).

- I don't think the idea will survive contact with the FAA. If they don't shoot you down with a local ruling/interpretation, then they'll just modify the words of the existing reg to meet their obvious intent: " no greater than 55 knots when in level flight or climbing."
No, there's really not anything strictly "e" about this, except that in an ICE engine, the work to implement it reliably would be akin to creating a fadec system from scratch, but for an e-plane, it'd be as simple as connecting your speed controller to a computer and adjusting parameters. You've already got the software built in for it.

The FAA says that 55kts is not a speed limit, you are allowed to fly faster (even in level flight). That is, unless they recently made it illegal for ultralights to pull out of dives, right?

As for safety, you still have FAA-approved power, so you can still handle a stall from a flat orientation. And if you make a mistake and pull back rather than pitch forward (or if you are at risk of colliding, so you suddenly pull up), then you will have bonus power to hopefully cover up for your goof up.
 

BBerson

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The power could be increased proportional as the stick is pulled back. That should limit speed.
It would only work when the boost button is held down and the stick pulled back.
 

Grimace

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The power could be increased proportional as the stick is pulled back. That should limit speed.
It would only work when the boost button is held down and the stick pulled back.
That's kind of what I was thinking with the button. Maybe a "trigger" on the grip could work.

I like the idea of going off of stick position. I need to think it through, but that could make sense. In a sense it's even "cheatier" than I was thinking, but it also would be fairly simple to implement.
 

Grimace

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Maybe simpler is better.

How about a system that cuts back power to my hypothetical 25kw whenever speed is over 54kts.This would allow for a HUGE climb rate. 1200fpm would be awesome in an ultralight powered-glider! And that extra power could then also be used for stall recovery, go arounds, etc.

At first I thought this would be a safety hazard, but it's actually not. Anything wrong with just limiting it based on airspeed?
 
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raumzeit

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Interesting. I've had daydreams along these lines for past half-year or so. My daydream-scheme would adjust the throttle 100% setting dynamically to the aircraft's attitude vector (not its AOA).

But wider to this subject of pushing luck with 103 definitions I don't know if I'd do that in today's political climate. There's a couple things in society that I believe are imperiling the freedom we have in the space already;

1) Powered parachutes. Those guys are dropping out of the sky like flies, the space is full of sketchy equipment purveyors, and it's one wrong VIP's kid or some-such auguring in from the whole space getting the Karen treatment.

2) Drones. Part 103's goals are safety of the public, not the pilot. I can build a drone easily with off-the-shelf parts today that is way bigger and faster than 103 aircraft requirements and fly it in places where a 103 aircraft gets called in/pilot goes to jail. That dissonance can't last forever.

So I don't know how much I'd go poking the bear developing Clintonian throttle-control schemes to get around 103 definitions trying to build a hot-rod. Karen is coming already, don't invite her friends. I'm with you in spirit, but just my two-cents there.
 
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