# How much interest would there be in an Ultrasonic Altimeter for ultralights?

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#### Himat

##### Well-Known Member
I kind of wonder where the pilots are. Its called peripheral vision.
And there you in a roundabout way point at the big marked.
The pilot do only have vision on a computer screen or 3D goggles.

Actually, to the seaplane pilot I think a acoustic close range altimeter can be useful.

#### Pops

##### Well-Known Member
Log Member
Back when I was a student pilot my instructor let me use the landing light for my first night landing, after that I was not allowed to land at night time with the landing light because he said landing lights can burn out. So I was taught a smooth water seaplane landing for a night landing without landing lights. I had to used it one time when I had a Cherokee 140 with the landing light in the nose bowl where it is close to the engine vibration. Yes, he was also a seaplane instructor + a sailplane instructor.

Dan

#### recmob

##### Well-Known Member
Perhaps, but land over completely glassy water and you would change your mind With insurance costing 3 times land aircraft rates, its cheap insurance. Every one I rebuilt that 'goes swimming', is in the neighborhood of $15,000.00 to fix. There is NO peripheral vision when landing on glassy water, and that's our main focus - to help seaplane pilots. My main point wasn't the cost. Its how much design / testing goes into doing what your looking at to come up with a reliable unit. We've already been there / tested that, trust me if you move forth you will find out too.$2450.00, yikes! That's almost what I paid for my entire airplane. At that price I think it's truly a solution in search of a problem, especially if you're marketing it to ultralights and homebuilts.

Not me, I have no use for such a thing.

Dana

#### Himat

##### Well-Known Member
I really can't be believe that a reasonable solution for the landing flare can't be found for less that $2,450. The Dambusters Lancasters used a pair of angled spotlights that overlapped when at the right altitude. With all the amazing technology available today for modest cost, I bet you could use a pair of laser pointers, a camera and a phone or tablet (or Arduino mini-computer) to do the same thing. Or manybe hack a laser tape measure? If you can make the unit by tens of thousands annually it can be cheaper. Trouble is that a custom made electronic circuit board is something like US$100 minimum to make if you only buy some thousand a year. Then you have to recover the development cost. If it is possible to use a commercial available circuit board, just a proper box, connectors and cabling can amount to a hundred US dollars. It is possible to get I cheaper, but that involves a lot of work sourcing the parts. And it's no good idea to go cheap by going down in quality on an airplane. Then there is the sensor, acoustical, optical or radio frequency. Even if adapted from something else the sensor is probably the single most expensive item of the hardware.

#### Dana

Staff member
The ultrasonic camera sensor is cheap, around $10 IIRC. But either way, a device such as this can be a cheap toy that works most of the time, or the expensive$2450 device that you can rely on. If you can't rely on the cheap one, then you better be able to land without it, and if you can land without it, why would you buy it unless it's really cheap (unless you just like gadgets)? OTOH, considering that TSO'd radar altimeters are in the $10K range, I suppose$2450 might make sense for a $50-100K experimental seaplane, and I can understand that development costs for a reliable unite could well justify that cost. Though electronics are so cheap and lightweight nowadays I suspect you could build a cheap double or even triple redundant unit for less than a single utterly reliable one... Dana #### BJC ##### Well-Known Member HBA Supporter ... I suppose$2450 might make sense for a $50-100K experimental seaplane, and I can understand that development costs for a reliable unite could well justify that cost. Dana Their LSA ASTM certified airplanes are in the$125,000 to $160,000 range. BJC #### Himat ##### Well-Known Member Though electronics are so cheap and lightweight nowadays I suspect you could build a cheap double or even triple redundant unit for less than a single utterly reliable one... Dana There are a few catches. - The cheap triple redundant unit better not have a common failure mode on all subunits. - The sensors better not interfere with each other both at normal operating and possible failure modes. The last one might be the most difficult or expensive to get around. #### Dana ##### Super Moderator Staff member Their LSA ASTM certified airplanes are in the$125,000 to $160,000 range. But then you'd need a TSO'd instrument, wouldn't you? Are there any LSA certificated seaplanes yet? I could see the Icon people wanting to put such a device in their planes. - The sensors better not interfere with each other both at normal operating and possible failure modes. The last one might be the most difficult or expensive to get around. Good point. Dana #### BJC ##### Well-Known Member HBA Supporter But then you'd need a TSO'd instrument, wouldn't you? Are there any LSA certificated seaplanes yet? I could see the Icon people wanting to put such a device in their planes. Dana I don't think that LSA ASTM certification requires TSO'ed instrumentation. Perhaps someone here who has researched the issue knows. As to LSA amphibians, see post #28. Or take this shortcut: SeaRey Sport, Rotax 912S (Certified) BJC #### Wanttaja ##### Well-Known Member BJC said: Their LSA ASTM certified airplanes are in the$125,000 to $160,000 range. But then you'd need a TSO'd instrument, wouldn't you? Actually, TSO'd equipment doesn't matter. The owner of a Special Light Sport Airplane cannot change or add any equipment without the manufacturer's approval. So your market would be Ex-AB aircraft and Experimental Light Sports, unless you convinced the LSA manufacturer to approve it. And they don't need a TSO to give it the OK. Ron Wanttaja #### gtae07 ##### Well-Known Member Actually, TSO'd equipment doesn't matter. The owner of a Special Light Sport Airplane cannot change or add any equipment without the manufacturer's approval. So your market would be Ex-AB aircraft and Experimental Light Sports, unless you convinced the LSA manufacturer to approve it. And they don't need a TSO to give it the OK. Ron Wanttaja Yes, there are several LSA's out there using non-TSO equipment right from the factory--see RV-12 S-LSAs with the option of a G3X touch or Skyview touch. #### SVSUSteve ##### Well-Known Member Typical pilots, you guys are blowing a simple idea into a huge discussion. The OP said it would be nothing more than a toy to play with in the cockpit. That close to the ground, your average pilot has zero business having "nothing more than a toy to play with". There are better things to do...uh, like flying the freaking airplane. It's an ultralight so you don't need anything more than a basic set of instruments. If you don't have the skills to handle that, then you need to spend that$2500 developing a relationship with a CFI and not on a crutch.

NOTE TO EVERYONE ELSE: Yes, I know it's ironic that it's me saying this of all people.

Can you count from 30 to zero faster than an ultralight on approach can fall out of the sky? Can you keep up with that count while you are trying to land that ultralight? I'm thinking it could get real confusing real quick while a tone would be much easier to follow
Can you tell me why you'd be focusing on a tone while you're "falling out of the sky" or why you would be "falling out of the sky" on an approach unless you've botched it and stalled? If you're dropping faster than it takes for the system to enunciate "30, 20, 10..." then you are probably descending close to 600 ft/min (figuring one second per annunciation....10 ft/second....etc and so on) and that could be an issue given how intolerant of hard landings most ultralights are.

Oh, and one other thing...you're not having to "count" and most people are going to mentally process hearing "30, 20, 10.." faster than they are going to recognize a particular tone. There's a reason why they don't use tonal systems in airliners or helicopters.

I am with CluttonFred. I'm sure there's a better option than \$2450 but I'm also sure that it's not trying to figure out whether you're hearing C# or D-flat.

#### cluttonfred

##### Well-Known Member
HBA Supporter
Points well taken, Steve, about training and practice vs. gadgets. If you were to use some sort of poor man's radar altimeter to help time the flare, l do think that a simple audio warning is a great way to keep your head up flying the plane rather than looking down at the instruments. It need not be terribly elaborate for the use being described--just a single, beep, unvarying in tone or duration, with the interval between beeps decreasing with height. Maybe 60 beeps per minute (one per second) at 100 feet increasing to 120 bpm (two per second) at 50 feet, 240 bpm (four per second) at 25 feet and a steady tone at a few feet above your ideal flare height. The last value would be adjustable and set by practicing landings over non-glassy water to get it just right.

#### Himat

##### Well-Known Member
Can you tell me why you'd be focusing on a tone while you're "falling out of the sky" or why you would be "falling out of the sky" on an approach unless you've botched it and stalled? If you're dropping faster than it takes for the system to enunciate "30, 20, 10..." then you are probably descending close to 600 ft/min (figuring one second per annunciation....10 ft/second....etc and so on) and that could be an issue given how intolerant of hard landings most ultralights are.
Good observation.
System range 30 feet/ ten meters.
Three annunciations before you hit ground.

I see two real uses, in a floatplane where the pilot is easing slowly down due to visual that gives poor depth perception.
Or in a UAV autopilot as a system cross check on GPS altitude.

Now, if anyone build them a VTOL plane such a device could come handy too.

#### SVSUSteve

##### Well-Known Member
Points well taken, Steve, about training and practice vs. gadgets. If you were to use some sort of poor man's radar altimeter to help time the flare, l do think that a simple audio warning is a great way to keep your head up flying the plane rather than looking down at the instruments. It need not be terribly elaborate for the use being described--just a single, beep, unvarying in tone or duration, with the interval between beeps decreasing with height. Maybe 60 beeps per minute (one per second) at 100 feet increasing to 120 bpm (two per second) at 50 feet, 240 bpm (four per second) at 25 feet and a steady tone at a few feet above your ideal flare height. The last value would be adjustable and set by practicing landings over non-glassy water to get it just right.
If you're going to make it adjustable (or even if you're not), it's just as simple to make it give you an vocal call out as to make it produce a tone. Stop and think about how many things you could conceivably mistake for that beep.

#### gtae07

##### Well-Known Member
If you're going to have something beeping, then it would be far better for that thing to be an audio AOA indicator (like the Dynon system). Height you can judge much more readily (excluding certain things like glassy water); AOA and signs of stall can be subtle depending on the airplane.

#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
Stop and think about how many things you could conceivably mistake for that beep.
Don't think a beep, think a constant but varying tone like a vario in a glider. Rate information is better communicated to a human in analog form than digital. Once the rate has been stabilized and a specific number or an end point, like the runway surface is the goal, then digital data is better.

An analogy from American car culture: Tachometer used in drag racing for shifting. The analog sweep of the dial preparing the driver for the digital shift light. The starting line lights are all digital because the rate of countdown is established by the second light - no anticipation needed, just good timing.

As you point out, if the rate of decent hasn't been stabilized at a reasonable level at or below 30 feet neither system is going to be of much use.

#### SVSUSteve

##### Well-Known Member
Rate information is better communicated to a human in analog form than digital.
Rate of descent isn't probably the best warning for ground proximity. It's potentially useful to have it start shrieking if you exceed a certain rate of descent (think the "SINK RATE!" alarm on a GPWS). What was originally proposed should probably be thought of more akin to the "wake up"/"pull your head out of your ***" alerts on an airliner. I think we have two camps viewing the device measuring two distinct things and good for two different applications. A rate of descent alarm is useful to avoid CFIT. A simplistic ground proximity system is good for avoiding either a late or early flare but given how wide open most cockpits on ultralights are, I am really not seeing the need.

There might be some utility for putting both functions in one system but then again, given how many fields have trees around them, I am curious how a system would react to the sudden change in "altitude that would come from passing over trees, approach lights, etc.

I see your point about variometers. Then again, I can't stand the sound they make. It's like nails on a chalkboard to me every time I have ever heard one in a video.

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