Taildragger brake adjustments

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blanston12
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Taildragger brake adjustments

Post by blanston12 »

I have a question for the expert developers here. I was trying out By Craig Richardson's HE-51 in P3D recently and was very impressed by it, I liked everything about it except when I tried to land it and apply the brakes, any small application of the brakes would cause the tail to jump upwards so I went down the runway tapping on the brakes, releasing when the tail started to climb and re-applying when the tail came back on the ground, eventually I ran out of runway and crashed.

So my question is this, is there a way to adjust the config of the aircraft to reduce tendency of a tail dragger to flip over tail first when the brakes are applied without throwing off the balance of the aircraft in flight?
Joe Cusick,

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Dev One
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Re: Taildragger brake adjustments

Post by Dev One »

Don't have the model, but there can be at least two problems for nosing over. The first is that the contact points for the mainwheels are too far aft, the second is that in the [brakes] section 'toe_brakes_scale' is set too high. Its a scalar on the .air file braking value. Reduce that first.
As for the Contact point, point.0 is the centre wheel (or skid), the first value after the = sign is the type of device, where 1 = a wheel, 2 = a scrape point & 3= a skid. Using a skid applies a greater drag when in contact with ground.
point.1 & point.2 are the mainwheels, with the next value after the type of device being the distance fore or aft of the datum. Now this is easy if the datum is set for 0,0,0 earlier in the aircraft.cfg as a positive value is forward of that datum & negative rearward - are you still with me?
One really should position the mainwheels for a taildragger by projecting a line normal to the a/c datum line through the 0,0,0 datum & then through the contact point when drawn in your 3 view of the a/c, then measure the dimension along the ground line with the tail wheel (or skid) sitting on the deck. Simple really but difficult to describe in words, so the answer here is to cheat & increase that value by say 0.1 feet until one is happy with the result. BTW I hope that when braking you are holding full elevator up!
Empty weight vertical C of G position can also play a part......
Good luck
Keith

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blanston12
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Re: Taildragger brake adjustments

Post by blanston12 »

Hi Keith,

Yes I follow you and will give that a try.

To be honest the idea of pulling back on the stick when landing was counter intuitive to me, as I don't want to go back up, but as I think about it, it makes sense, thanks!
Joe Cusick,

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Re: Taildragger brake adjustments

Post by Tako_Kichi »

As Keith said pulling back on the stick to 'nail' the tail to the ground while braking is common practice on tail draggers. You need to ease the stick back, not yank it back, in order to prevent the aircraft taking off again. Getting the flaps up before braking and applying back stick can also help to prevent inadvertent take-offs too.

In addition to the above FSX only has one setting for brakes and that has to cover everything from a Piper Cub to a 747 and sometimes developers can get it wrong (or simply can't be bothered to get it right) when it comes to brake values. Very often you will see the brake scalar set to '1' which is way too high for anything other than a large commercial jet.
Larry

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blanston12
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Re: Taildragger brake adjustments

Post by blanston12 »

Since I don't use rudder pedals with brakes the only settings I have is either on or off, I have several times had to adjust the max brake force down to lessen the likelihood of it going nose over, but for this AC there did not seem to be a setting that would stop it from tipping and still stop it. Hopefully with better technique and by adjusting the wheel position and/or center point until its safe we can find this AC a place in the hanger.
Joe Cusick,

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Re: Taildragger brake adjustments

Post by Tako_Kichi »

If the line does not exist in the [Brakes] section you can always add it yourself and then save the aircraft.cfg file.

The line in question is:

toe_brakes_scale = XXX - where XXX is the value you require (1 is the default but it should be less than 1 in most cases).

You can also add differential braking if you want to, even without rudder pedals with toe brakes. By twisting your stick for rudder control and applying the brakes you can get left or right braking independently as the brakes are tied into the rudder position.

The line to add in that case is:

differential_braking_scale = XXX - where XXX is the value you require (1 is the default but it should be less than 1 in most cases).

Hope that helps.
Larry

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blanston12
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Re: Taildragger brake adjustments

Post by blanston12 »

Thanks for all the information.

I reduced the toe_brakes_scale from .9 to .6.5 and that combined with raising the flaps on landing and pulling back on the elevators once the tail was on the ground made for a nice save landing.

My second surprise was that some bi-planes have flaps!

Thanks for the help.
Joe Cusick,

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Re: Taildragger brake adjustments

Post by Dev One »

Now I think there is an adjustment for braking strength in the .air file - Block 1101 line 13 *Braking Strength - Max (ft/sec^2*2048?) = 32767 on my current aircraft which is the maximum allowed & it seemed to help decrease the braking distance. Haven't experimented more with that setting though.
Glad you have found a suitable setting so not nosing over any more.
As for Bipes with flaps I think Swordfishes had them & maybe Gladiator? My DH 90 Dragonfly does!
Keith

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