Is your Airspeed Indication Accurate? Here's How to Tell
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- čas přidán 5. 07. 2024
- This is something every airplane owner should know, but most especially those who have built or are flying experimental aircraft. I've seen and heard a lot of misconceptions out there, hopefully this helps clarify some things.
Apologies for my congested voice - I did this while sick! I think I managed to edit out most of the coughs and sniffles!
00:00 Intro
00:57 Misconceptions
01:29 IAS to TAS calculation
2:56 indicated airspeed system review
4:01 Pitot-Static system check
5:19 Static Port location
8:31 Airspeed Verified with GPS?
9:34 Wind Triangle
10:00 How your avionics generates info for you
12:27 How to really confirm if your airspeed is accurate
16:05 Check stall speeds
17:55 Ending - Auta a dopravní prostředky
Extremely well done. I like your academic approach in your videos and you asking "why" and "how".
Good explanation, I have a Europa XS kit plane and recall the factory needed tp spend some time testing to get a accurate location for pitot and static port.
Thank you for the morning dose of knowledge. I sincerely appreciate it and I really enjoy your other videos. Keep them coming!
Good information. Thank you.
I am putting my OAT on the wing. Also, I am thinking about combining both the rear and front static ports into one blended setting. I will likely play with it several ways. I do have both static ports installed.
Yeah, I'm going to move my OAT probe out to under the wing, too.
I follow your channel because I hope (one day) to build an airplane and sling tsi is a leading candidate. This video was great! I've only ever flown certified airplanes and - apart from pitot icing - it never occurred to me that IAS might be inaccurate.
This opens up a whole host of things that I didn't think about before when it came to building an airplane. Thanks for sharing this.
Thx Mike, I hope to have my maiden flight before the end of this year. Static ports back on the fuselage and OAT under the wing. Will share my numbers.
I bet that's the winning combination. Good luck!
Thanks Mike very helpful. I have ordered the Vans static kit and will install it towards the rear as Evan now recommends. But I think your point about the OAT probe may actually the most important. I don't want mine anywhere near the NACA duct/ engine heat.
Mike, thanks for the useful video. My home build TSi was the first in the UK to have the new staic port locations so we did extensive testing. We found the that TAS is about 3 Kts higher than IAS in approach configuration. Meaning I fly to 62 KIAS (Rather than book of 65 KIAS over the fence). We also found that switching to internal static port reduced IAS by 2 to 5 Kts.
TAS being 3 knots higher than IAS does not mean you should fly 3 knots slower IAS for approach. TAS will always be higher than IAS any time you're above sea level density altitude. That's normal and doesn't mean your IAS is wrong.
Also very strange that airspeed reads lower when internal static port is selected. Normally it's the opposite.
I really appreciate this type of content Mike! Thank you for putting this together and for the knowledge review. Once my plane is completed I will run through these tests and report the results. I am still trying to determine where to put my static port as I have a QB kit and its a bit more involved to place it in the tail area at this point. I did purchase the RV static ports but am curious if I put the static port in the newer location near the cowling, what is the recommended part to use for that area?
I'm not sure what the new recommended part is. Best to contact Sling Technical.
Excellent video great information. See you at airventure
I can't make it this year, but Evan will be there. He's flying in a new Kitfox that he just built with the Rotax 916iS in it.
@@OneAlphaMike to bad you can't make it.. but sounds like his kitfox is badass
Thanks thanks thanks.....
Thanks for the video Mike. My static ports are in the new location… I flew today and was showing GS of 134 in the G3X, then I looked at my iPad info (connected to a sentrix unit) and it was also reading 134 GS. I was pretty happy with that… your thoughts?
All you did was compare groundspeed from two different GPS sources? That tells you nothing about the accuracy of your airspeed indication.
I went with the Evan location halfway back the tail and my speed seemed absolutely correct. I calculated that via the triangle method and by verifying my stall was what sling says it should be
Perfect!
Interesting and informative topic. So we should subtract ~3 knots from the cruise speeds you mention in your "Sunset flight to Tampa" video?
For my airplane (experimental, not a Sling) I flight tested to find the stall IAS and then multiplied that by 1.3 to determine approach speed. But since I'm not sure how much pitot error there is between stall AOA and approach AOA, it's not an exact science.
Yes, subtract 3 knots or so from my TAS to get the "True True" Airspeed. 😁
Mike, I didn't quite understand why the IAS reads faster if I'm using the static pressure from inside the cabin. I'm seeing the opposite. I'm still using inside static pressure, have Installed the new static ports up front but haven't connected them yet as I have to put in paperwork before I make the change.
Hi Ashok! You can find this in several sources, such as the FAA's Instrument Flying Handbook. "Due to the venturi effect of the air flowing around the fuselage, the air pressure inside the flight deck is lower than the exterior pressure." See page 5-3, here: www.goldsealgroundschool.com/goldmethod/library/ifh-chap5-7.pdf
So, the lower static pressure measured there being subtracted from the total pressure in the pitot tube leads to a higher result, leading to erroneously high airspeed indication.
In my plane I have an alternate static source switch, and when I switch to the internal source I can see my altitude and airspeed increase. You say you're seeing the opposite, but you also say you haven't connected the external static ports. So, how are you comparing it?
What is best static port location on a sling TSI and why is your stall speed 7kn off? Its a lot of diff compared to the POH, right?
@EvanBrunye says the best location is back on the aft fuselage using the Vans static port kit, which is basically hollowed out rivets.
I have my static ports in the factory recommended location with the factory-provided shrouds, yet my speed is still off, especially at the low end. The only thing I did different was use a different model static port than what they now recommend. So, either that's the problem, or the new recommended location is not good.