Standby Instruments for Primary Use?

[dans2992]

Is there any reason I could not replace the AI in my six-pack with this?

http://sarasotaavionics.com/avionics/sai340-quattro

Supposedly it's only a "standby" instrument, but does that mean I would have to just keep and relocate my existing AI? What makes this inferior to a "primary" AI?

Also, it's interesting that this one is sooo much more expensive, but the only feature that seems to be added is a compass (and an extra 0.7" on the display). Am I missing something?

http://sarasotaavionics.com/avionics/trilogy-esi-1000

 

[bnt83]

I'm not seeing why you can't. Start matching up the TSO approvals on high end mechanical instruments and they match those of the cheaper glass unit.

 

[poadeleted20]

Is there any reason I could not replace the AI in my six-pack with this?

http://sarasotaavionics.com/avionics/sai340-quattro

If the TSO gets approved (it's listed as "pending"), and given its internal 2-hour battery backup, I see no reason why not. However, you'd have to see what it says in the TSO to be sure.

Also, it's interesting that this one is sooo much more expensive, but the only feature that seems to be added is a compass (and an extra 0.7" on the display). Am I missing something?

http://sarasotaavionics.com/avionics/trilogy-esi-1000

That one does not appear to have an internal backup battery, so for IFR operations you'd have to keep your existing vacuum AI somewhere in the panel as backup in event of electrical failure.

I'd discuss this with the Airworthiness folks at your local FSDO to see if they have any guidance on point.

 

[dans2992]

Are there different TSOs for "primary" and "backup" instruments?

Also, and I realize there are a lot of unknowns here, but currently I have a mechanical AI with two vacuum pumps. Would this probably be more (or less) reliable than that setup? I know there is no way to say for sure, but just looking for opinions.

 

[JimNtexas]

Is a TSO'd ADI required for part 91?

 

[poadeleted20]

Is a TSO'd ADI required for part 91?

It has to be an FAA approved part if it's going to be used to meet the 91.205(d) requirement in a production certified aircraft, and a TSO is the usual way you see that other than OEM equipment.

 

[poadeleted20]

Are there different TSOs for "primary" and "backup" instruments?

I haven't researched the issue, but the TSO's to which they're looking to get certified are listed in the linked material, so you can do that research yourself if you're interested.

 

[rbridges]

Supposedly it's only a "standby" instrument, but does that mean I would have to just keep and relocate my existing AI? What makes this inferior to a "primary" AI?

yeah, you still have to keep your primary instruments. Just my ignorant opinion, but I think it boils down to certification. Until it's approved for primary, you can't get rid of the gauges it replaces.

 

[Pedals2Paddles]

An attitude indicator and slip indicator is not on the required equipment list in 91.205. So I don't see why you couldn't do this. You could remove your ASI completely and still be legal.

You could not use it to replace the ASI and altimeter though. Those are required in part 91.

 

[Turningfinal]

An attitude indicator and slip indicator is not on the required equipment list in 91.205. So I don't see why you couldn't do this. You could remove your ASI completely and still be legal.

You could not use it to replace the ASI and altimeter though. Those are required in part 91.

It is required in 91.205(d) assuming OP is using his aircraft under IFR.

 

[poadeleted20]

I've taken the time to do the research. The first unit says it's being TSO'd to the following standards:
TSO-C2d (Type B ) - Airspeed Indicators
TSO-C3e - Turn and Slip Insrument
TSO-C4c - Bank and Pitch Instruments
TSO-C10b (Type I) - ALTIMETER, PRESSURE ACTUATED, SENSITIVE TYPE
TSO-C113a - Airborne Multipurpose Electronic Displays
TSO-C201 (A5 HX T7) - Attitude and Heading Reference Systems (AHRS)

None of those standards limit the devices certified under them to "standby" or "backup" roles. The only issue would be the backup power source in event of loss of aircraft electrical power, and I think the internal 2-hour battery would cover that one. Of course, the FAA does require a backup AI, airspeed, and altimeter for any PFD (in case the PFD itself fails), but once the TSO process is complete, I see no reason you couldn't install the Sandel SAI340 as your primary flight display as long as you keep another AI, airspeed, and altimeter in your panel as backups (just like you see with systems like the Garmin and Avidyne PFD's).

The L-3 unit has a similar TSO list (TSO-C2d, TSO-C4c, TSO-C6d, TSO-C10b, TSO-C113, TSO-C106) covering airspeed, pitch and bank, gyro-stabilized magnetic direction (slaved compass), altimeter, multipurpose display, and AIR DATA COMPUTER. I see nothing about a backup power supply, but you'd need backup AI/airspeed/altimeter no matter what anyway.

I'd be interested to hear what AFS-300 would have to say about installing these as primaries with mechanical backup instruments instead of the other way around.

 

[RotorAndWing]

I'd be interested to hear what AFS-300 would have to say about installing these as primaries with mechanical backup instruments instead of the other way around.

Shouldn't be an issue as most everything being produced today doesn't have any mechanical instruments installed.

 

[poadeleted20]

Shouldn't be an issue as most everything being produced today doesn't have any mechanical instruments installed.

First, at least at the light GA level, that isn't true. The G1000 and Avidyne planes being produced all have three mechanical backups (AI, airspeed, altimeter) to meet the FAA requirement in 14 CFR 23.1311(a)(5):

(5) For certification for Instrument Flight Rules (IFR) operations, have an independent magnetic direction indicator and either an independent secondary mechanical altimeter, airspeed indicator, and attitude instrument or an electronic display parameters for the altitude, airspeed, and attitude that are independent from the airplane's primary electrical power system. These secondary instruments may be installed in panel positions that are displaced from the primary positions specified by Sec. 23.1321(d), but must be located where they meet the pilot's visibility requirements of Sec. 23.1321(a).

Further, the electronic display systems in those planes are specifically certified for use as the primary instruments, while the two under discussion are specifically advertised as standby/backup devices. So, I'd still like to hear what AFS-300 has to say about installing them as the primaries with mechanical backups somewhere else in the panel.

That said, the Sandel device with its 2-hour internal battery appears to meet this standard as a backup for a primary EFIS. The L-3 device says nothing about independent power, so I don't see it as being a legal backup for an EFIS unless it has a capability not mentioned in the linked page, but it would still be fine as a non-required backup for mechanical primary instruments.

 

[Pedals2Paddles]

It is required in 91.205(d) assuming OP is using his aircraft under IFR.

The slip/skid is. Not the AI. Nowhere in part 91 is an attitude indicator required. So removing his old AI and using this, as far as I can tell, is of no consequence to anything.

So, if you are VFR only, you could use this to replace your AI and slip skid, which you aren't required to have anyway. If you're IFR, you can use it to replace only the AI.

 

[Turningfinal]

First, at least at the light GA level, that isn't true. The G1000 and Avidyne planes being produced all have three mechanical backups (AI, airspeed, altimeter) to meet the FAA requirement in 14 CFR 23.1311(a)(5):

The Cessna Corvalis TTx does not have any mechanical backup instruments. It uses another EFIS for backup, obviously isolated from the primary electrical system. G2000 primary with L-3 (I think) backup.

 

[Turningfinal]

The slip/skid is. Not the AI. Nowhere in part 91 is an attitude indicator required. So removing his old AI and using this, as far as I can tell, is of no consequence to anything.

So, if you are VFR only, you could use this to replace your AI and slip skid, which you aren't required to have anyway. If you're IFR, you can use it to replace only the AI.

91.205(d)(8).

How else would you interpret:
(8) Gyroscopic pitch and bank indicator (artificial horizon).

?

 

[poadeleted20]

The slip/skid is. Not the AI. Nowhere in part 91 is an attitude indicator required. So removing his old AI and using this, as far as I can tell, is of no consequence to anything.

Neither slip/skid nor AI are required for VFR. Both are required for IFR. See 14 CFR 91.205(b) and (d).

So, if you are VFR only, you could use this to replace your AI and slip skid, which you aren't required to have anyway. If you're IFR, you can use it to replace only the AI.

For IFR, you still need a slip/skid. 14 CFR 91.205(d)(4). Of course, if you leave the old TC or T&B in the panel, you don't need a second slip/skid, but if that old instrument goes when you do the conversion, you're going to need a slip/skid integrated in the new electronic instrument.

 

[poadeleted20]

The Cessna Corvalis TTx does not have any mechanical backup instruments. It uses another EFIS for backup, obviously isolated from the primary electrical system. G2000 primary with L-3 (I think) backup.

Thanks. Of course, the Corvalis TTx is a very small portion of the light GA EFIS-equipped fleet, and the only C400's in which I've flown had the mechanical backups.

 

[RotorAndWing]

First, at least at the light GA level, that isn't true. The G1000 and Avidyne planes being produced all have three mechanical backups (AI, airspeed, altimeter) to meet the FAA requirement in 14 CFR 23.1311(a)(5):

(5) For certification for Instrument Flight Rules (IFR) operations, have an independent magnetic direction indicator and either an independent secondary mechanical altimeter, airspeed indicator, and attitude instrument or an electronic display parameters for the altitude, airspeed, and attitude that are independent from the airplane's primary electrical power system. These secondary instruments may be installed in panel positions that are displaced from the primary positions specified by Sec. 23.1321(d), but must be located where they meet the pilot's visibility requirements of Sec. 23.1321(a).

So the way I read this is a non mechanical instrument may be used as a backup.

Further, the electronic display systems in those planes are specifically certified for use as the primary instruments, while the two under discussion are specifically advertised as standby/backup devices.

What differentiates primary versus standby is the power source.

So, I'd still like to hear what AFS-300 has to say about installing them as the primaries with mechanical backups somewhere else in the panel.

Wouldn't hurt, but you could get that answered at the FSDO level. The PAI of the installing shop could make that determination, and you would get it quicker.

 

[poadeleted20]

91.205(d)(8).

How else would you interpret:
(8) Gyroscopic pitch and bank indicator (artificial horizon).

?

91.205(d)(8) doesn't apply to VFR operations. See 91.205(b), which does not include that requirement. OTOH, for IFR, you need both slip/skid and AI -- see 91.205(d)(4) and (8).

 

[poadeleted20]

So the way I read this is a non mechanical instrument may be used as a backup.

Agreed, no question. But the OP was asking about using it as the primary, and I'd run that past AFS-300 before having the shop install it.

What differentiates primary versus standby is the power source.

Do you have something which says that? I thought it was instrument location, per 14 CFR 23.1321(d).

(d) For each airplane, the flight instruments required by Sec. 23.1303, and, as applicable, by the operating rules of this chapter, must be grouped on the instrument panel and centered as nearly as practicable about the vertical plane of each required pilot's forward vision. In addition:]
(1) The instrument that most effectively indicates the attitude must be on the panel in the top center position;
(2) The instrument that most effectively indicates airspeed must be adjacent to and directly to the left of the instrument in the top center position;
(3) The instrument that most effectively indicates altitude must be adjacent to and directly to the right of the instrument in the top center position; and
(4) The instrument that most effectively indicates direction of flight, other than the magnetic direction indicator required by Sec. 23.1303(c), must be adjacent to and directly below the instrument in the top center position; and
(5) Electronic display indicators may be used for compliance with paragraphs (d)(1) through (d)(4) of this section when such displays comply with requirements in Sec. 23.1311.

Wouldn't hurt, but you could get that answered at the FSDO level. The PAI of the installing shop could make that determination, and you would get it quicker.

With what it says in 23.1321, if the manufacturers hadn't said "standby" so many times in their promotional material, I wouldn't think twice about using these as primaries once the TSO's are approved -- the reg itself pretty clearly says it's OK. As for asking the FSDO rther than AFS-300, that's the proper channel to do it anyway. I suspect the FSDO folks may ask AFS-300 before they give you an answer, as using something advertised as a "standby" or "backup" instrument as your primary instrument probably falls in the "weird question" department about which local FSDO's generally don't like to stick out their necks in writing. But yes, if the FSDO did give me an answer in writing, that would do fine for me.

 

[RotorAndWing]

Agreed, no question. But the OP was asking about using it as the primary, and I'd run that past AFS-300 before having the shop install it.
Do you have something which says that? I thought it was instrument location, per 14 CFR 23.1321(d).
With what it says in 23.1321, if the manufacturers hadn't said "standby" so many times in their promotional material, I wouldn't think twice about using these as primaries once the TSO's are approved -- the reg itself pretty clearly says it's OK. As for asking the FSDO rther than AFS-300, that's the proper channel to do it anyway. I suspect the FSDO folks may ask AFS-300 before they give you an answer, as using something advertised as a "standby" or "backup" instrument as your primary instrument probably falls in the "weird question" department about which local FSDO's generally don't like to stick out their necks in writing. But yes, if the FSDO did give me an answer in writing, that would do fine for me.

There's a difference between "advertised as" and what the technical specifications call for.

A simple phone call to the manufacturer should clear up any questions.

 

[Witmo]

It has to be an FAA approved part if it's going to be used to meet the 91.205(d) requirement in a production certified aircraft, and a TSO is the usual way you see that other than OEM equipment.

Upon reading 91.205 nowhere does it specify that all required equipment listed for various operations has to be FAA approved. It does say "unless that aircraft contains the instruments and equipment specified in those paragraphs (or FAA-approved equivalents) for that type of operation, and those instruments and items of equipment are in operable condition." 91.205 does state certain equipment specifically must be "approved" such as approved lighting systems or approved seat belts or approved shoulder harnesses or an approved DME, so why doesn't the regulation say "approved instruments? It would be a simple thing to specify all instruments listed need to be FAA approved but that's not the way it's written. So if you want to replace say, a gyroscopic artificial horizon with an electronic one, the regulation requires the electronic one to be an FAA approved "equivalent" of a gyrosopic AI. If you want to replace a TSOd gyroscopic AI with a non-TSOd gyroscopic AI that is in operable condition, I see no prohibition by the wording in 91.205. As with many things, the airworthiness of a part is in large part a determination made by the installing mechanic. If the regulation doesn't specifically call out a requirement for a TSOd component, it's a judgement call by the installing mechanic whether or not the part is airworthy.

 

[dtuuri]

Upon reading 91.205 nowhere does it specify that all required equipment listed for various operations has to be FAA approved. It does say "unless that aircraft contains the instruments and equipment specified in those paragraphs (or FAA-approved equivalents) for that type of operation, and those instruments and items of equipment are in operable condition."

Isn't "type of operation" the same as "kind of operation" under Part 23.1525? It reads:

§23.1525 Kinds of operation.

The kinds of operation authorized (e.g. VFR, IFR, day or night) and the meteorological conditions (e.g. icing) to which the operation of the airplane is limited or from which it is prohibited, must be established appropriate to the installed equipment.
​

I think the mechanic needs to verify the conformity of the installed equipment to the original type certificate. Changing the limitation from VFR to IFR ought to take more than a mechanic's authorization, I'd think. I would bet the FAA would only allow TSO'd equipment to do that. Off hand, I don't know if CAR 3 or antique aircraft are limited in the same way as Pt 23.1525 though.

dtuuri

 

[Witmo]

Isn't "type of operation" the same as "kind of operation" under Part 23.1525? It reads:

§23.1525 Kinds of operation.

The kinds of operation authorized (e.g. VFR, IFR, day or night) and the meteorological conditions (e.g. icing) to which the operation of the airplane is limited or from which it is prohibited, must be established appropriate to the installed equipment.
​

I think the mechanic needs to verify the conformity of the installed equipment to the original type certificate. Changing the limitation from VFR to IFR ought to take more than a mechanic's authorization, I'd think. I would bet the FAA would only allow TSO'd equipment to do that. Off hand, I don't know if CAR 3 or antique aircraft are limited in the same way as Pt 23.1525 though.

dtuuri

The mechanic does not change a limitation on an aircraft. The type certificate states whether a standard category aircraft is approved for VFR or IFR operations. An aircraft that is not limited to VFR operations only need have the required IFR equipment in 91.205 and static\transponder inspections to operate under IFR. The question is whether all the required equipment need be OEM or TSOd. I don't see 91.205 requiring TSOd replacements for many of the required instruments or equipment.

It's different for Part 135 and 121 operations. I know that even headsets have to meet TSO's for the more strict regulations governing public transport for hire.

 

[dtuuri]

The question is whether all the required equipment need be OEM or TSOd. I don't see 91.205 requiring TSOd replacements for many of the required instruments or equipment.

That's what I'm saying, doesn't the mechanic need to confirm the Pt 205 equipment is OEM or TSO'd as an alternative?

dtuuri

 

[poadeleted20]

Upon reading 91.205 nowhere does it specify that all required equipment listed for various operations has to be FAA approved.

You're right. The requirement to use approved parts in production certified aircraft is not in Part 91. That's covered in Part 21 and the AC's deriving therefrom. You use either the same item as listed in the type certificate/equipment list or a TSO'd or otherwise approved replacement. Keep in mind that a flight instrument like an AI is not a "standard part (such as a nut or bolt) manufactured in compliance with a government or established industry specification".