FDAI rate indicators correct?

Dozerman

New member
Joined
Mar 21, 2021
Messages
2
Reaction score
0
Points
1
Location
SPB
Hi! I read Аpollo systems manual and find this:
In the simulator, pointers work the other direction around as it seems to me
010.JPG
 
Last edited:

indy91

Addon Developer
Addon Developer
Joined
Oct 26, 2011
Messages
994
Reaction score
288
Points
78
Hmm, I think it's possible that we got this wrong. It would be the same in the LM then I expect. I guess it's one of those things we just never question, because it's always been like this. Sort of like the abort light which for a long time was a button in NASSP (did they press it in the Apollo 13 movie?), but actually is just a light. Let me do some more research to confirm this, before I fully believe we got this wrong all along.
 

Thespacer

Active member
Joined
Oct 26, 2019
Messages
96
Reaction score
42
Points
33
FWIW, and on the assumption the shuttle design inherited from Apollo, I note the following from page 2.7-5 of the Space Shuttle Crew Operations Manual (https://www.nasa.gov/centers/johnson/pdf/390651main_shuttle_crew_operations_manual.pdf):

“The rate scales are not labeled on the Orbit PFD. These pointers are “fly to” in the sense that the RHC must be moved in the same direction as the pointer to null a rate.“

And in relation to the att error needles in a later paragraph: “These needles are also “fly to,” meaning that the flight crew must maneuver in the direction of the needle to null the error.” Note the use of “also.” Of course the att error needles in Apollo are fly-to as well.

My brain is not looking forward to the adjustment, if indeed there is something to be adjusted!
 

GLS

Well-known member
Orbiter Contributor
Addon Developer
Joined
Mar 22, 2008
Messages
4,539
Reaction score
751
Points
138
AFAIK the Shuttle was "fly-to" all the way to the last OI (used in the last 5 flights or so) when for some reason they changed it... :rolleyes:
The text above and the fact that tons of stuff in the Shuttle came from Apollo (e.g., the LM FDAI was used as the Shuttle ADI), I'd say the rate needles should be "fly-to".
 

ggalfi

Active member
Joined
May 31, 2020
Messages
42
Reaction score
65
Points
33
Location
Budapest
I know this is a Block I FDAI, but it is another evidence on the "fly to" side.
However, if this would be changed, it will be like relearning cycling but with reversed steering. Or at least learning the Russian-style artificial horizon after the Western one.
 

Dozerman

New member
Joined
Mar 21, 2021
Messages
2
Reaction score
0
Points
1
Location
SPB
However, if this would be changed, it will be like relearning cycling but with reversed steering. Or at least learning the Russian-style artificial horizon after the Western one.
I fly in DCS on Soviet and USA planes and helicopters. No problems with different styles artificial horizons.
 

ggalfi

Active member
Joined
May 31, 2020
Messages
42
Reaction score
65
Points
33
Location
Budapest
I fly in DCS on Soviet and USA planes and helicopters. No problems with different styles artificial horizons.
It is interesting, because when I began to practice instrument flying on DCS's MiG-21 I did have some problems when it came to quick interpretation of the attitude indicator. Nothing extreme, just sometimes a bit of confusion for a fraction of a second. However when I've got my real life IR training and one day after take off it turned out that the aritficial horizont was unreliable. We decided with my instructor to continue with the task and I'll do the ILS approaches on turn indicator instead of the AH. What was surprising that though the turn indicator works in the "Russian" style, even on a Cessna, I didn't have any problem with it and it didn't have any sensible impact on the accuracy of my approaches. But I'd attribute it to the fact that the "Wendezeiger" is a totally different instrument than the AH, and in my brain there were no burnt-in motoric reflexes associated with it. Or maybe I'm much more focused when I fly a real plane than when I'm playing with flight sims :)
But anyway, I'm definitely "pro-realism", and it seem to me very likely that the current behaviour of the rate indicators are working erroneously in NASSP, so it ought to be corrected.
 

ggalfi

Active member
Joined
May 31, 2020
Messages
42
Reaction score
65
Points
33
Location
Budapest
I mean I volunteer to do this change, if you are all agree. Just want to make sure no one is working on this already.
 

indy91

Addon Developer
Addon Developer
Joined
Oct 26, 2011
Messages
994
Reaction score
288
Points
78
I will take care of it. Haven't fully decided yet what the best place to change polarity is (panel code or electronic display assembly...). I also haven't found a definite source yet if it works the same way in the LM. Once I have I'll change it in both spacecraft at once.
 

STS

Active member
Joined
Feb 1, 2009
Messages
407
Reaction score
26
Points
43
Location
Vigo
Website
orbisondas.es
o_Oo_O

I don´t see the logic or understand FDAI rate indications, if the rate indicators are wrong in all the way around.

I think It´s more logical, easier to follow, and easier to understand, in the way they are currently implemented. They show in wich direction your rates are going. So if the Roll arrow moves to the right, you are banking to the right and you (depending on what you are doing) need to kill that rate by rolling to the left, with the purpose of moving that arrow to the left and centering it.

I think it will be like learning to drive the CSM again, but we should be really sure if the current implementation is wrong.
 

GLS

Well-known member
Orbiter Contributor
Addon Developer
Joined
Mar 22, 2008
Messages
4,539
Reaction score
751
Points
138
I will take care of it. Haven't fully decided yet what the best place to change polarity is (panel code or electronic display assembly...). I also haven't found a definite source yet if it works the same way in the LM. Once I have I'll change it in both spacecraft at once.
Can the FDAIs be driven by the AGC? If so, then the answer (or more info) should be in the code...
 

indy91

Addon Developer
Addon Developer
Joined
Oct 26, 2011
Messages
994
Reaction score
288
Points
78
AGC can only drive the attitude error needles, which I am pretty sure have the correct behavior already. They currently move in the opposite direction from the rate needles, which seems to contradict the documentation about it. Attitude comes directly from the IMU, so it doesn't go through the AGC. Attitude rates come from the attitude gyros. The main issue with the location of the upcoming change is a bit of inconsistency between the 2D and 3D panel code. The virtual cockpit has the rate needles animated, while on the 2D panel they are drawn on the bitmap. So I was just going through the code in my head to see in which place I would have to do the least amount of changes, that's all.
 
  • Like
Reactions: GLS

ggalfi

Active member
Joined
May 31, 2020
Messages
42
Reaction score
65
Points
33
Location
Budapest
After crunching many docs on LM to find conclusive evidence but no avail, I decided to give a try and ask the man who has the most knowledge about the LM (or at least who I'm aware of). So out of the cold I've asked Fred Haise on the LM FDAI rate indicators, and to my great surprise he answered very quickly. Here is his answer in it's entirety: "I recall it was fly to but the FDAI rate display didn't play a big role in landing. The key instruments were the landing radar providing altitude and horizontal motion over the ground. Next was the read of "h dot" o sink rate, and the out the window view to avoid obstacles"
 

indy91

Addon Developer
Addon Developer
Joined
Oct 26, 2011
Messages
994
Reaction score
288
Points
78
Well it's great to hear it from the man himself, although he almost seemed to dodge your question and rather wanted to talk about lunar landings instead of a specific technical detail. :D

thewonderidiot found something about the LM in the LM G&C Data Book (https://archive.computerhistory.org/resources/access/text/2019/01/102789076-05-01-acc.pdf)


And in an Apollo training document (for the CSM) it has some handwritten comments on the page about the FDAI.

Fly to comments
If spacecraft yaws right, the yaw rate needle moves left.

All of these sources are quite early (about 1967), except for the AOH, the version of Volume 1 we have is from 1969. And all sources are in agreement, the attitude rate is fly-to. So I guess I won't take long anymore to convince myself to make the change...
 

n72.75

Addon Developer
Addon Developer
Tutorial Publisher
Donator
Joined
Mar 21, 2008
Messages
2,033
Reaction score
428
Points
98
Location
Biddeford ME
Website
www.adabsurdumpublishing.com
Yeah, Fred Haise counts as a pretty authoritative source on the matter.

Thank you @Dozerman for bringing this to our attention in the first place. And of course, thanks to @ggalfi for contacting Fred Haise.
 

indy91

Addon Developer
Addon Developer
Joined
Oct 26, 2011
Messages
994
Reaction score
288
Points
78
The polarity of the FDAI attitude rate needles has now been inversed. I hate it. :D But it was the correct decision, as all documentation we found pointed to this being the case.
 
Top