I think I’ve read somewhere before about the GTX OAT not being that accurate. Ours seems to match the METAR on the ground on a standard-ish day, but I haven’t checked it when the temperature has been at or close to zero. I agree that an always-on and easily visible OAT readout is probably not a bad idea, rather than having to keep an eye on the transponder which is over on the right hand side of the panel.
No it doesn’t need to be an original part from decades ago. Per NCO, however, the equipment required by NCO.IDE shall be an approved* installation (don’t remember the proper wording, I guess you find that at the beginning of NCO.IDE). This means any available STC (e.g. OAT gauge) would work.
Thanks for that – that makes things easier. I had seen that wording in NCO.IDE, and the bit in the AMC about the wristwatch being acceptable, but I hadn’t quite figured out whether that only applies to the equipment required by NCO, or whether it extends to the equipment required in the flight manual, which uses the word ‘installed’. So far as the OAT is concerned I suppose it makes no difference provided it has an STC, but it would be useful it the wristwatch could also satisfy the AFM requirement for an ‘installed’ clock!
Thanks again for all the help.
Surely there must be a concession (CS-STAN, anyone?) which covers installing an OAT instrument as a Minor Mod, provided the instrument itself complies with TSO or ETSO?
On an N-reg you can screw anything into the panel as a Minor Alteration provided (taking the simple case here) it is TSOd, there is no autopilot connection, it isn’t “EFIS”…
Obviously the installation needs to follow standard procedures e.g. a load analysis and the installation of a circuit breaker if necessary.
An STC is only for a Major Mod…
Another approach may be if the TB20 TC includes the installation of some instrument e.g. the Davtron 303 which was installed on a lot of TB20s. You can install anything approved on the TC – see e.g. here. Sometimes the said item is restricted by airframe S/N e.g. S/N 2000+ only, and that for example prevents installing 2 × GNS in a pre-GT TB20 (you can do it but under EASA it is a big Major mod).
Couldn’t see OAT instrument in CS-Stan issue 3, there is one SC about replacing engine instrument (steam gauge) and one (SC 401) about flight instruments but OAT is listed in neither.
Btw, SC 401 lists the clock and states again that the clock doesn’t ned to be TSO’d
That sounds like a sensible approach, but I’m finding it hard to find any OAT indicators that are ETSOd. E.g. Davtron’s web site doesn’t mention ETSO (nor any FAA approvals for that matter) for any of their instruments from what I can see, nor with a bit of Googling have I managed to find any others that do either. The list of EASA ETSO authorisations only has two OAT sensors on it: one is part of the Avidyne Entegra EFIS, and the other is related to another air data computer product that looks like it is intended to be connected to an integrated EFIS system, rather than a standalone gauge. Is ETSO the right set of standards it would need to adhere to? I still need to read up on CFR23 (which according to the TCDS is the certification basis for the TB20) to see if that says any more on instrument certification.
To Peter’s point around fitting something that is already on the TB20 type certificate, this was my initial instinct when I first started to look at this problem. The OAT indicator in the Socata parts catalogue (which looks very much like the Davtron M303, although they don’t call it that by name) has a validity for all aircraft serial numbers, but then says apres mod 151 which I believe means for GT models only. Ours is most definitely not GT! However I’ve just stumbled across something in the ‘options and kits’ catalogue called the ‘Peckly Outside Air Thermometer’ which looks a lot like an inoperative temperature gauge we have in our panel, which I’d always assumed was installed aftermarket. If they are one and the same thing, then getting that fixed might be the easiest way to resolve the OAT problem with no further modification approval needed. Although oddly there is no probe for it under the port wing where it should be, nor any sign of there every having been one there.
Btw, SC 401 lists the clock and states again that the clock doesn’t ned to be TSO’d
Thanks for that. I’ve found that reference now. It does also say that it the new clock needs to be installed in the same location in the panel, which on the TB20 is in the yoke, where it will be neatly covered by my (non ETSO-certified) iPad 
I think I probably need to take the aircraft and its logbooks to an avionics shop and let them try and figure out what to do.
Peter – the TB20 in question is the one you had to edge your wingtip past this morning at Shoreham. There was more space there than it probably looked like from your vantage point Hope you had a good flight!
Hello Sam I can’t write much because I have just the phone
But good luck finding a shop which understands the regs… There are people here who do and hopefully they can help.
imperialsam wrote:
I’ve heard it said that Part NCO supersedes older IFR equipment carriage requirements
It does. It’s the actual spirit of the whole of NCO, many requirements are no longer hardwired MELs but up to you as PIC to decide your means of compliance (and backups) to perform the flight in appropriate conditions, as mentioned by huv above on the time-keeping device. It’s not true for everything, obviously, but the minima are lower than they used to.
boscomantico wrote:
The placard is not made depending whether some equipment required for IFR is installed or not.
Sure they do. Or did, at a time when a hard MEL was required.
AlexTB20 wrote:
If someone tells my I need it when I have 4 microphone equipped headsets
The rear seat position can’t transmit, so they’re no help
AlexTB20 wrote:
1 portable transceiver
This one does.
tmo wrote:
How so?
According to Swiss regulations, we need two 8.33 coms, at least that is what I have been told. As we have avionic work upcoming I will check again, but apparently the Swiss have gold plated their IFR requirements yet again.
Mooney_Driver wrote:
tmo wrote: How so?According to Swiss regulations, we need two 8.33 coms, at least that is what I have been told. As we have avionic work upcoming I will check again, but apparently the Swiss have gold plated their IFR requirements yet again.
Please check with them, that might now be true anymore, for example:
Even UK CAA are changing their stance on this from end of Feb 2021 – if you fly IFR in a SEP, one radio is OK.
arj1 wrote:
Please check with them, that might now be true anymore, for example:
Für Lufträume, in welchen 8.33 kHz Kanalabstand verlangt ist, müssen beide VHF COM über 8.33 kHz Kanalabstand verfügen
This TM is still valid.
