I’m sure you have all heard someone assert that his plane does 50, 60, 70 or more mph. When pressed on how this speed was measured, you’ll usually get answers that indicate a LOT of windage. If only we had an air speed instrument for model planes.
This diminutive package uses the same differential pressure sensing as on full-scale aircraft. Airspeed indicators measure the difference between ambient air pressure and total pressure in flight due to the plane’s forward motion (“ram air”) captured with the pitot tube. Obstructing the free flow of air of these tubes will compromise accuracy, as will off-center tube placement. The “How-Fast” captures the highest speed flown.
The Static Tube has four small holes drilled in it and is sealed on one end, the Pitot Tube is open on both ends:
The unit mounts in the wing
Drawing courtesy of Winged Shadow Systems
or on the wing for flat wings – the key is to make sure that the two tubes are NOT in the prop wash and that they extend at least ½” from the wing – the Static Tube’s small holes must extend at least ½” from the wing. You must ensure that they are parallel to the fuselage and level. The open parts of the tubes can be shortened if needed. Also note that you can shorten or lengthen the tubing between the instrument and the tubes – as long as they are not kinked, length should not be an issue.
Reading the unit requires that you wave your finger over the LED to trigger its read-out BEFORE you turn the power off. Once triggered, it flashes steady for about 4 seconds, then the LED flashes the speed – for example, for 123 mph you’ll see one flash, pause, two flashes, pause, then 3 flashes. Two digit speeds, eg 46, will report as four flashes, pause, then six flashes; zero is a quick double flash. Once you read this speed, it will be stored in memory and can be recalled later, even after powering down.
Drawing courtesy of Winged Shadow Systems
I found the finger waving requires some practice to get right. First you should have the LED pointing squarely at the sun or a light bulb – it’s triggered by the difference between light and shadow. I found one way to get a reading is to use a flashlight – hold it close to the LED and then wave; the waving cycle requires some experimentation – practice this before you mount it. I shot a video (blurry) of this process – the readout flashes 46 mph – HERE.
Performance
After getting the finger waving down, I tested the “How Fast” by mounting the unit on my car’s mirror and driving 60 mph on the highway. I found the unit recorded an average of 56 mph. This is within the accuracy range according to my query on this to Winged Shadow Systems:
“From our tests on a wide variety of installations, in the range of typical model flight speeds (30 MPH to 120 MPH) I’d say you can expect a peak reading well within 5 MPH of your true airspeed.”
Accurate mounting of the tubes is critical to accuracy:
“A unique (and potentially large) source of errors is the mounting of the Pitot and Static tubes. Careful alignment of the tubes directly into the direction of flight will give excellent results. Miss-pointed tubes or locating the tubes in the prop blast can create significant errors. Of course, clogged or pinched tubes can make the readings useless. Since the How Fast makes offset readings at power-up and again when the report is activated, strong winds into the sensor probes at these times can also cause minor errors.”
I mounted the How Fast on one of my foamies by taping the tubes to the flat wing and found it’s moving quite nicely with speeds in the high 30s.
Conclusions
Short of a radar gun (really expensive) or a measured course, measuring a plane’s speed anectdotally is not terribly accurate. The How Fast looks like a reasonable solution – while not cheap (what is in this hobby?) at $45, sharing it among a few flyers or buying it by a club to share among its members to determine plane speed with some accuracy could be one way to lower cost, although you can’t discount “bragging rights”.
Many thanks to Dave at Winged Shadow Systems for sending this our way to test out. Overall, a nice package!
“How Fast” Model Aircraft Airspeed Instrument
I’m sure you have all heard someone assert that his plane does 50, 60, 70 or more mph. When pressed on how this speed was measured, you’ll usually get answers that indicate a LOT of windage. If only we had an air speed instrument for model planes.
The good guys at Winged Shadow Systems were nice enough to send a sample of their How Fast Model Aircraft Airspeed Instrument to try out.
Key Features
km/h, 10 flight memory
This diminutive package uses the same differential pressure sensing as on full-scale aircraft. Airspeed indicators measure the difference between ambient air pressure and total pressure in flight due to the plane’s forward motion (“ram air”) captured with the pitot tube. Obstructing the free flow of air of these tubes will compromise accuracy, as will off-center tube placement. The “How-Fast” captures the highest speed flown.
The Static Tube has four small holes drilled in it and is sealed on one end, the Pitot Tube is open on both ends:
The unit mounts in the wing
or on the wing for flat wings – the key is to make sure that the two tubes are NOT in the prop wash and that they extend at least ½” from the wing – the Static Tube’s small holes must extend at least ½” from the wing. You must ensure that they are parallel to the fuselage and level. The open parts of the tubes can be shortened if needed. Also note that you can shorten or lengthen the tubing between the instrument and the tubes – as long as they are not kinked, length should not be an issue.
Reading the unit requires that you wave your finger over the LED to trigger its read-out BEFORE you turn the power off. Once triggered, it flashes steady for about 4 seconds, then the LED flashes the speed – for example, for 123 mph you’ll see one flash, pause, two flashes, pause, then 3 flashes. Two digit speeds, eg 46, will report as four flashes, pause, then six flashes; zero is a quick double flash. Once you read this speed, it will be stored in memory and can be recalled later, even after powering down.
I found the finger waving requires some practice to get right. First you should have the LED pointing squarely at the sun or a light bulb – it’s triggered by the difference between light and shadow. I found one way to get a reading is to use a flashlight – hold it close to the LED and then wave; the waving cycle requires some experimentation – practice this before you mount it. I shot a video (blurry) of this process – the readout flashes 46 mph – HERE.
After getting the finger waving down, I tested the “How Fast” by mounting the unit on my car’s mirror and driving 60 mph on the highway. I found the unit recorded an average of 56 mph. This is within the accuracy range according to my query on this to Winged Shadow Systems:
“From our tests on a wide variety of installations, in the range of typical model flight speeds (30 MPH to 120 MPH) I’d say you can expect a peak reading well within 5 MPH of your true airspeed.”
Accurate mounting of the tubes is critical to accuracy:
“A unique (and potentially large) source of errors is the mounting of the Pitot and Static tubes. Careful alignment of the tubes directly into the direction of flight will give excellent results. Miss-pointed tubes or locating the tubes in the prop blast can create significant errors. Of course, clogged or pinched tubes can make the readings useless. Since the How Fast makes offset readings at power-up and again when the report is activated, strong winds into the sensor probes at these times can also cause minor errors.”
I mounted the How Fast on one of my foamies by taping the tubes to the flat wing and found it’s moving quite nicely with speeds in the high 30s.
Short of a radar gun (really expensive) or a measured course, measuring a plane’s speed anectdotally is not terribly accurate. The How Fast looks like a reasonable solution – while not cheap (what is in this hobby?) at $45, sharing it among a few flyers or buying it by a club to share among its members to determine plane speed with some accuracy could be one way to lower cost, although you can’t discount “bragging rights”.
Many thanks to Dave at Winged Shadow Systems for sending this our way to test out. Overall, a nice package!