G5 airspeed indicator setup mph / knots

Salty

Salty

Touchdown! Greaser!
Joined
Dec 21, 2016
Messages
13,416
Location
FL
Display Name
Display name:
Salty
When my G5 PFD was installed, it was configured for mph as the owners manual for the plane uses mph for all speed discussions, and the analog airspeed indicator is in mph (on the big outside ring, it does have knots in small letters on the inside). I assumed this was a regulatory requirement, and frankly, since I had been flying the plane in "mph" anyway I let it go.

Anyway, now that I'm doing IFR training, it always seems to be a source of confusion when I'm talking mph, and everyone else is thinking knots. I'm toying with the idea of switching the G5 over to knots.

Is there any regulatory advice on this? Can this be done legally, especially since it's not the primary airspeed indicator, and the primary airspeed indicator does have knots on it (inner tiny numbers)
 
I thought the G5 could be knots or MPH as pilot's choice since the G5 is not primary for ASI.
 
NordicDave said:
I thought the G5 could be knots or MPH as pilot's choice since the G5 is not primary for ASI.
Click to expand...
I'm hoping that's true, but it wasn't my understanding. I'm hoping my understanding was incorrect.
 
Oh, there's also placarding inside the plane in mph. My instinct tells me it's not legit.
 
Salty said:
When my G5 PFD was installed, it was configured for mph as the owners manual for the plane uses mph for all speed discussions, and the analog airspeed indicator is in mph (on the big outside ring, it does have knots in small letters on the inside). I assumed this was a regulatory requirement, and frankly, since I had been flying the plane in "mph" anyway I let it go.

Anyway, now that I'm doing IFR training, it always seems to be a source of confusion when I'm talking mph, and everyone else is thinking knots. I'm toying with the idea of switching the G5 over to knots.

Is there any regulatory advice on this? Can this be done legally, especially since it's not the primary airspeed indicator, and the primary airspeed indicator does have knots on it (inner tiny numbers)
Click to expand...

The FAA approved installation instructions define what it must be set to. Without these instructions it would not have received approval...
 
Per the G5 STC install manual:

Note 1: Set configuration values and units to match the values indicated in the appropriate AFM and document settings in the space provided.
Note 2: If the aircraft has no AFM set the values as determined by the existing placards, instrument bugs or instrument markings.
Note 3: Existing placards related to airspeed limitations must be retained.

I would personally interpret that as requiring it to be set to MPH in your situation.
 
The Install Manual will tell you what's required. That said, what do you think the likelihood is that (a) it would create a dangerous condition or (b) that anyone other than you would ever notice if you changed it?
 
Salty said:
When my G5 PFD was installed, it was configured for mph as the owners manual for the plane uses mph for all speed discussions, and the analog airspeed indicator is in mph (on the big outside ring, it does have knots in small letters on the inside). I assumed this was a regulatory requirement, and frankly, since I had been flying the plane in "mph" anyway I let it go.

Anyway, now that I'm doing IFR training, it always seems to be a source of confusion when I'm talking mph, and everyone else is thinking knots. I'm toying with the idea of switching the G5 over to knots.

Is there any regulatory advice on this? Can this be done legally, especially since it's not the primary airspeed indicator, and the primary airspeed indicator does have knots on it (inner tiny numbers)
Click to expand...

One would think on an airplane as expensive as a G5 there would be more modern instrumentation utilizing knots rather than mph!!!
Ok. Sorry. Guess that was out of line but I couldn't resist:goofy:
 
Makes friends with a tech at an avionics shop. Others may know better, can't a plane be re-placarded in knots with the right log book entry?
 
As per the install manual you have to set the airspeed in mph if your AFM is in mph and/or the aircraft has placards in mph. However, you can set everything else in knots and nm if you wish (GS, dist, etc.). This is the case for my AA-5. The only time it is clumsy for me is when setting up for approach at 90 kt...oops, 105 mph.

Well, also when I'm calculating TAS, I have to do a quick conversion to knots on the whiz wheel if I want winds aloft in kt. Unless I'm at 7500 feet, then on a standardish day mph IAS is approximately TAS kt. Or close enough for government work.
 
Salty said:
When my G5 PFD was installed, it was configured for mph as the owners manual for the plane uses mph for all speed discussions, and the analog airspeed indicator is in mph (on the big outside ring, it does have knots in small letters on the inside). I assumed this was a regulatory requirement, and frankly, since I had been flying the plane in "mph" anyway I let it go.

Anyway, now that I'm doing IFR training, it always seems to be a source of confusion when I'm talking mph, and everyone else is thinking knots. I'm toying with the idea of switching the G5 over to knots.

Is there any regulatory advice on this? Can this be done legally, especially since it's not the primary airspeed indicator, and the primary airspeed indicator does have knots on it (inner tiny numbers)
Click to expand...
did you ever find out if you could do it or not?
 
ryan heiner said:
did you ever find out if you could do it or not?
Click to expand...
You can do it, but you would not be following the regulations. As chemgeek mentioned, the install documentation for the STC requires you to configure airspeed in the G5 to match that of the legacy airspeed indicator and what the aircraft manual specifies.

If you did it, you would technically not be in compliance with the STC and your aircraft would not be airworthy, but actually making the change is a trivial task.
 
Salty said:
You can do it, but you would not be following the regulations. As chemgeek mentioned, the install documentation for the STC requires you to configure airspeed in the G5 to match that of the legacy airspeed indicator and what the aircraft manual specifies.

If you did it, you would technically not be in compliance with the STC and your aircraft would not be airworthy, but actually making the change is a trivial task.
Click to expand...

Let's be realistic - if you get busted by the FAA (or anyone else for that matter) because your G5 ASI is set to MPH vs KTS, you were gonna get busted for SOMETHING anyway (they're really, really fishing at that point). It's such a trivial issue that virtually nobody is ever going to notice. It's like jaywalking - acknowledge that it's technically against the rules, that the risk is just about 1 tick above 0 and move on with your life.
 
bradg33 said:
Let's be realistic - if you get busted by the FAA (or anyone else for that matter) because your G5 ASI is set to MPH vs KTS, you were gonna get busted for SOMETHING anyway (they're really, really fishing at that point). It's such a trivial issue that virtually nobody is ever going to notice. It's like jaywalking - acknowledge that it's technically against the rules, that the risk is just about 1 tick above 0 and move on with your life.
Click to expand...
I don’t disagree. The only reasons I didn’t say that myself were

1. I don’t like telling people it’s ok to break the rules

2. I think there is a good reason for this rule. Especially if someone else ever flies your plane.
 
bradg33 said:
Let's be realistic - if you get busted by the FAA (or anyone else for that matter) because your G5 ASI is set to MPH vs KTS, you were gonna get busted for SOMETHING anyway (they're really, really fishing at that point). It's such a trivial issue that virtually nobody is ever going to notice. It's like jaywalking - acknowledge that it's technically against the rules, that the risk is just about 1 tick above 0 and move on with your life.
Click to expand...
Problem is, you can probably say that about most pilot deviations with the only differentiation being what one considers trivial.
 
midlifeflyer said:
Problem is, you can probably say that about most pilot deviations with the only differentiation being what one considers trivial.
Click to expand...

Totally fair point. Obviously, everyone has to determine for themselves what they consider trivial and what their risk tolerance is. If I were flying for a living, I'd like have a much smaller list of things I consider trivial given my own personal risk tolerance (get dinged by the FAA, possibly lose or impact the way to earn a living).
 
Mine has the same ASI as @Salty described. Main scale in MPH, secondary in KTS. When I bought the plane, it had a G500, scaled in KTS. The TCDS has all airspeeds in MPH, but with KTS in parentheses after each entry. I added a G5, which is also calibrated in KTS. Not an advocate of rule breaking, but I think the parentheses allow it. Think Salty's might be a similar vintage Piper? (early '70's)
 
Hang 4 said:
Mine has the same ASI as @Salty described. Main scale in MPH, secondary in KTS. When I bought the plane, it had a G500, scaled in KTS. The TCDS has all airspeeds in MPH, but with KTS in parentheses after each entry. I added a G5, which is also calibrated in KTS. Not an advocate of rule breaking, but I think the parentheses allow it. Think Salty's might be a similar vintage Piper? (early '70's)
Click to expand...
It was a Mooney at the time. And no knots in the poh.
 
You must log in or register to reply here.
Back
Top