Radio Altimeter

[safir365]

Hi guys,

I noticed an issue with the airplane, I don't know if is related to any x-plane limitation.
I found that the gap between the 10 ft radio altimeter callout and the touchdown is just too big. In real life it comes almost instantly after.
The radio altimeter antennas are located it the forward fuselage of the 737 so that it should normally read 2-4 ft at main gear touchdown then -2 ft when
lowering the nose wheel and the main struts are compressed. I did a test with the ixeg where I kept playing with the pitch (up to 10 degrees) during take off roll below Vmu to see if I could
make the RA indication vary with the pitch but it kept a constant -2 ft indication as long as it was on the ground.

Can you please try to solve this issue for the next update?

Edited February 13, 2017 by safir365

[frumpy]

The time between the 10ft callout and touchdown depend on your flare. You can slam into the runway or

stay in ground effect for a longer period.

The 737-300 is 110ft long. The RA antenna is between the maingear and the nose. I approximated the

antenna to be at 30ft from the nose. Landing attitude is about 5°. Taking a rectangular triangle,

alpha is 5°, the lower side b is 30, that means x is ~2.6ft. Thats the -2 we see after lowering the nose

on the ground. Should be about 0 when touching down. I think for normal operation this is fine.

 

Concerning the 10° pitch: well, for this the position of the antenna needs to be modelled. Technically

you are right. Personally I don't care, because this is not something I look for when taking off

or touching down.

[Litjan]

I agree with most of your findings (except for the time between 10 and touchdown, that depends on how hard you like to land ).

We are NOT going to implement a custom radar altimeter model that takes antenna position and body angle into account. We are using X-Plane´s internal radar altitude variable, and are cueing our radar altitude readout and callouts off of that.

I applaud your attention to detail, but there is a point where we have to say no .

Cheers, Jan

 

[safir365]

1 hour ago, Litjan said:

I agree with most of your findings (except for the time between 10 and touchdown, that depends on how hard you like to land ).

 

Yeah I know what you mean. I fly the bus IRL so we don't have this problem .

My first flares with the ixeg were a bit high by 5ft, I had to get used to it. I'm sure you understand what I mean.

Thank you for the answer

[Morten]

Correct, this is a problem with XP's radio altimeter, not the callout.  Sent a bugreport to Austin some time ago. (RA will show "0" between 0-6' AGL) Makes you flare a bit early (like +6' high) and also will make auto land float a bit. We decided to wait and see if they fixed it for XP11, if not we'll fix it our selves.  Problem is, when we do, it will mess up everyones landings since people have been getting used to flaring late, so not sure it's a good idea  

M

Edited February 13, 2017 by Morten

[Tim013]

I knew there was a reason I make crappy landings.  I knew it couldn't be my skill set....LOL.

Tim