Taylorcraft air speed

[woodmw]

Re: Taylorcraft air speed

Here is a TAS calculator from GPS ground speed and heading:

http://www.csgnetwork.com/tasgpscalc.html

I fly a square box, i.e., four legs @ 90^o. Since the calculation only requires 3 legs, having the fourth leg allows four calculations. Then average. To be honest, just averaging the four legs gave results very close to this calculator. (< +/- 1 mph)

[Guest]

Re: Taylorcraft air speed

A straight out and back will not provide an accurate speed if there is any wind.

Hi Tom,

It will work IF you fly directly into the wind and directly down wind (180 degree turn).

It works because in one direction the wind speed adds directly to the ground speed and in the other direction it directly subtracts so the average of the ground speeds is the TAS.

Dave R

[Guest]

Re: Taylorcraft air speed

Mark,

I think I figured out why the triangle works.

At first it looks like too many unknowns for the number of equations but after you consider that 1) you know the TAS heading, 2) that the sum of sin^2 and cos^ =1 and 3) that the 90 degree turns merely flip signs of sin & cos terms or translate a sin to a cos then you end up with enough equations and unknowns.

I have not finished yet but it looks straightforward at 2:14 am and I think I could solve it later.

It ends up with a quadratic term but that's not too annoying.

Dave R

[Hank Jarrett]

Re: Taylorcraft air speed

Man you guys really like making the math hard! I like math, but not THAT Much! If you have a GPS you can fly a standard circle (DO NOT reference the ground!) and look for the aground speed to rise and fall. At the highest ground speed you will be flying a heading directly WITH the wind, at the lowest directly into the wind. Now fly each way and compare the ASI with the ground speed to determine the no wind speed. Don't forget to do another 360 after the two straight runs to make sure the wind didn't change enough to mess up the calculations.

Hank

[Hank Jarrett]

Re: Taylorcraft air speed

Man you guys really like making the math hard! I like math, but not THAT Much! If you have a GPS you can fly a standard circle (DO NOT reference the ground!) and look for the aground speed to rise and fall. At the highest ground speed you will be flying a heading directly WITH the wind, at the lowest directly into the wind. Now fly each way and compare the ASI with the ground speed to determine the no wind speed. Don't forget to do another 360 after the two straight runs to make sure the wind didn't change enough to mess up the calculations.

Hank

[Guest]

Re: Taylorcraft air speed

Man you guys really like making the math hard! I like math, but not THAT Much! If you have a GPS you can fly a standard circle (DO NOT reference the ground!) and look for the aground speed to rise and fall. At the highest ground speed you will be flying a heading directly WITH the wind, at the lowest directly into the wind. Now fly each way and compare the ASI with the ground speed to determine the no wind speed. Don't forget to do another 360 after the two straight runs to make sure the wind didn't change enough to mess up the calculations.

Hank

Hi Hank,

Very very clever!

I like it.

But I just had to know if the three leg with 90 degree turn course was real or an internet hoax , I think it is real.

Dave R.

[TimHicks]

Re: Taylorcraft air speed

Not germane to this conversation. But on the first flight of my '46 BC12-D after a total restoration and a C85 with a Sensenich 72x50 wood, my test pilot texted me this picture of the ASI

[Mark Bowden]

Re: Taylorcraft air speed

It is simplest just to do it, fly triangle, square or circle you will be close enough. Just fly it and average them up. No need to do any calculations.

It’s a fun excuse to go fly and be a test pilot.

Yes, as mentioned you cannot get a good TAS performance number by flying into and then with the wind. The headwind effect is greater than the tailwind effect.

The equations are a kind of cumbersome, I’ve seen them in some older post war text books. WWII really drove the need to figure out a way to get good performance numbers for accurate mission planning. Now a days you get to have calibrated pitot static booms on your flight test aircraft.

The multi-leg or circle route is just to negate most of the wind/course variabilities and the headwind greater than the tailwind effect. To compare your performance like Ray wants to do (bad rig to good rig) be consistent, fly the same route, same altitude and same power settings; lock those in. Avoid thermals and turbulence as you don’t want the climb & dive changes. They don’t energy balance either

For straight legs, you want the legs to be long enough so that the time it takes to get re-trimmed and stable on the new course leg is a fraction of the individual leg time.

[Hank Jarrett]

Re: Taylorcraft air speed

Hi Hank,

Very very clever!

I like it.

But I just had to know if the three leg with 90 degree turn course was real or an internet hoax , I think it is real.

Dave R.

I didn't actually run the numbers for that one (had to do that when I was getting my degree but have never done it since). As several have said with the speeds we fly the errors aren't that much if you just fly a square (more error from cross winds) or up and down wind (no cross wind error). Easiest is to just run the test flight very early in the morning when it is very calm out. You will see MUCH more error from not having a stable trim than from almost anything else. As one of the guys said avoid thermals and sink, it will really screw up your numbers too. Personally I ALWAYS look for thermals. Fly faster for free! ;-)

Hank

[Guest]

Re: Taylorcraft air speed

I didn't actually run the numbers for that one (had to do that when I was getting my degree but have never done it since). As several have said with the speeds we fly the errors aren't that much if you just fly a square (more error from cross winds) or up and down wind (no cross wind error). Easiest is to just run the test flight very early in the morning when it is very calm out. You will see MUCH more error from not having a stable trim than from almost anything else. As one of the guys said avoid thermals and sink, it will really screw up your numbers too. Personally I ALWAYS look for thermals. Fly faster for free! ;-)

Hank

The three leg with sequential 90 degree turns has a mathematical basis.

I don't believe that the triangle course does have a math basis.

That circular course with finding min and max ground speeds could be made into a TAS finding routine built into a GPS



p.s. 4/12/17 I was wrong about the triangle course it does have a math basis I was too dense to see initially.

[Guest]

Re: Taylorcraft air speed

It is simplest just to do it, fly triangle, square or circle you will be close enough. Just fly it and average them up. No need to do any calculations.

It’s a fun excuse to go fly and be a test pilot.

Yes, as mentioned you cannot get a good TAS performance number by flying into and then with the wind. The headwind effect is greater than the tailwind effect.

The equations are a kind of cumbersome, I’ve seen them in some older post war text books. WWII really drove the need to figure out a way to get good performance numbers for accurate mission planning. Now a days you get to have calibrated pitot static booms on your flight test aircraft.

The multi-leg or circle route is just to negate most of the wind/course variabilities and the headwind greater than the tailwind effect. To compare your performance like Ray wants to do (bad rig to good rig) be consistent, fly the same route, same altitude and same power settings; lock those in. Avoid thermals and turbulence as you don’t want the climb & dive changes. They don’t energy balance either

For straight legs, you want the legs to be long enough so that the time it takes to get re-trimmed and stable on the new course leg is a fraction of the individual leg time.

If what is in red is true then it has the same effect on the "circular" method that Hank mentioned, on the upwind/downwind method that J Stall mentioned and will also effect the other schemes as well.

Thus you cannot get a good TAS performance number by flying any method.

I am not sure I believe that but it is the logical end of it.

Dave R

[3Dreaming]

Re: Taylorcraft air speed

Hi Tom,

It will work IF you fly directly into the wind and directly down wind (180 degree turn).

It works because in one direction the wind speed adds directly to the ground speed and in the other direction it directly subtracts so the average of the ground speeds is the TAS.

Dave R

Dave, Here is an example. If you have a 60 mph airplane and a 30 mph wind. Your destination is 90 miles away. With a groundspeed of 30 miles per hour it will take 3 hours to get there. With the 30 mph tailwind it will only take 1 hour to get home, for a total of 4 hours. If you make the same 90 mile trip with no wind it will take you 1.5 hours each way for a total of 3 hours. The airspeed for the airplane will remain the same, but the average groundspeed will change because of the wind.

[Guest]

Re: Taylorcraft air speed

Dave, Here is an example. If you have a 60 mph airplane and a 30 mph wind. Your destination is 90 miles away. With a groundspeed of 30 miles per hour it will take 3 hours to get there. With the 30 mph tailwind it will only take 1 hour to get home, for a total of 4 hours. If you make the same 90 mile trip with no wind it will take you 1.5 hours each way for a total of 3 hours. The airspeed for the airplane will remain the same, but the average groundspeed will change because of the wind.

Hi Tom,

Agree

The average ground speed is the average of 30 mph outbound and 90 mph inbound or 60 mph. It is equal to the TAS that you started with.

J Stall stated that this method can be used to find the TAS.

If we flew this course and only recorded the flight time and distance and didn't even have an ASI we could calculate average ground speed and equate it to TAS.

I also noticed a typo in my original post.

I said "wind speed adds directly to the ground speed" but I meant to say "wind speed adds directly to the TAS to produce the ground speed".

Dave R

[Scott]

Re: Taylorcraft air speed

The headwind effect is greater than the tailwind effect.

Really? I think we've strayed a little off the flight profile !!

The effect on covering distance maybe greater but not the effect on speed.

If airspeed is constant and wind speed is constant, ground speed is equal to airspeed plus or minus the headwind or tail wind component respectively. (check your flight computer)

So if your airspeed is 90 and wind speed is 20, when flying directly into the wind subtract 20 flying directly downwind add 20. The impact of the wind on ground speed is the same (but opposite) in either direction. It is also the same and opposite for any 2 points 180 degrees apart on the compass as the tailwind and headwind components will be equal in magnitude.

So yes you can do a reasonable check of TAS using ground speed and opposing headings. (actually any two 180 opposing headings)

When you add the distance component, i.e. the return flight scenario, the wind still has the same equal and opposite impact of 20 on ground speed on both the outbound and inbound legs, but you spend more than half the total trip time at the slower ground speed, this is why the total time will be more than the same trip in calm conditions.

Flying to any destination is accomplished at your average ground speed. The average ground speed in 3Dreaming's example is 45 i.e. 3 hours at 30 and 1 hour at 90 (180/4=45). In the no wind scenario the average ground speed equals TAS (60) of course so you cover the total distance faster.

[Guest]

Re: Taylorcraft air speed

The average ground speed in 3Dreaming's example is 45 i.e. 3 hours at 30 and 1 hour at 90 (180/4=45). In the no wind scenario the average ground speed equals TAS (60) of course so you cover the total distance faster.

Hi Scott,

I don't think this part is correct.

In Tom's example the airplane ground speed is 30 out and 90 back.

The simple average is 60 same as TAS in his example.

That's not a coincidence, if you write the two equations and solve for TAS it comes out equal to the simple average of the two ground speeds.

Looks like you are doing a weighted average.

Dave R

p.s. ahhh... I think I see the confusion that is taking place. That part is just different than what I was thinking about there is nothing wrong with it. It's in what we each mean by "average ground speed" I mean only the average of the two speeds (out and back). The out speed is distance traveled out divided by flight time out or by GPS, similar for return. Average of those two is TAS always.

The other way to do "average ground speed is round trip miles (180) divided by total time (4), I don't mean that one but I see what you guys are saying now.

I should have said something like "the average of the ground speed calculated to the destination and the grounds speed calculated from the the destination" instead of just the average ground speed. My bad.