Stall warning inop, airworthy?

Mooney_Driver wrote:

Anyone who can not reckognize that an airplane which sinks uncontrollably with a high pitch attitude is in a stall condition doesn’t belong into a cockpit. Warning or not.

Whilst that may be true, many of them have flown 1,000’s of hours in various operators and are normally considered highly competent pilots. Ergo, study up on human factors and you’ll realise that whilst this is an attractive statement in theory, in practice you may become the next…

LeSving wrote:

It’s just that i’ts up to the PIC to determine if a stall and fuel indicator is required for the intended flight.

If they were part of the design intended to meet the airworthiness certification criteria then no, of course you cannot remove the stall warning and fuel indicators from the aircraft or have them unserviceable and still go fly. Unless there is an MEL that gives legal basis for dispatching with unserviceable equipment.

If the instrument was required for the IFR airworthiness certification, but not required for VFR airworthiness, then of course you can depart on an VFR flight. However the aircraft cannot be dispatched for IFR flying until the equipment is fixed.

Aviathor wrote:

So what you are saying is that a nav light or landing light is u/s the a/c is grounded unless released by a mechanic?

No, nav light and landing lights are covered as “equipment” in the CS. This equipment is covered by part NCO, and is not required for VFR day (under EASA regulations).

So what you are saying is that a nav light or landing light is u/s the a/c is grounded unless released by a mechanic?

LeSving wrote:

You were talking about autopilots and red map lights.

Yes, that autopilot failure grounded the aircraft and cabin (passenger) reading light caused a level 2 warning for being C/Fed while this wasn’t allowed. Again, their argument is that this kind of equipment is “standard equipment” That is equipment that is listed on the manufacturer equipment list is standard / (non optional). They argued, and I can see how they come to the conclusion, that the aircraft is only airworthy when it conforms to its design (standard equipment, TCDS, and thus also certification standard), when it doesn’t conform either their should be additional certificiation (STC or in some cases minor change) for the change in design.
Equipment that isn’t installed, or non functional but is listed as standard equipment should be serviceable to conform to the design or design changes.

DO NOTE: Avionics and some instruments are not part of this, that is optional equipment, carriage as required for the kind of operation (NCO)

Did you see that CS-23 example MEL lists stall warning as mandatory for every operation?

Jesse wrote:

According your suggestion, you design your aircraft to meet this requements, install that equipment required to become certified, and then you could remove all this equipement such as stall warning and fuel indicator as it is no longer needed???

That was not what I meant. Although I don’t see a reason why not, in principle. It’s just that i’ts up to the PIC to determine if a stall and fuel indicator is required for the intended flight. (Artificial) stall warning may very well be “required” for normal flights in certain types, while it’s just an unnecessary “nice to have addition” in others. It’s the same with fuel quantity. You don’t need to know the fuel quantity every minute of the flight if you are going to fly it 10 mins to the nearest repair shop. Obviously these items cannot simply be removed. You were talking about autopilots and red map lights.

Jesse wrote:

Though it seems the same applies to FAA according FAR 43.13B, see this Inspection Authorization Information Guide

14 CFR 91.213 (d) provides for the “properly altered condition” requirement:

An aircraft with inoperative instruments or equipment as provided in paragraph (d) of this section is considered to be in a properly altered condition acceptable to the Administrator.

LeSving wrote:

It would be interesting to see an explanation as to how they reach this conclusion. There is no mention about “standard equipment”, only required equipment.

This depends where you look. If you have a look at Part NCO, agreed. If you look at the aircraft equipment list by the manufacturer, it comes with standard equipment, and optional equipment. The aircraft has been certified with this equipment. standard equipment should be serviceable.

Do note that the stall warning is not part of the equipment section (Appendix F of CS-23 nor Subpart F of FAR-23). CS-23 does not indicate equipment needed for VFR / IFR etc either that is described in Part NCO, as indicated by you. The stall warning is part of Subpart / Appendix B (Flight section) of FAR-23/CS-23

LeSving wrote:

as it may specify all kinds of additional equipment that has to be airworthy when installed in an aircraft.

Ok, you design a new general aviation aircraft, you choose CS-23 as certification basis. Your design MUST meet the specifications from CS-23. It must have a stall warning, right? It also instructs to you have a fuel quantity indicator. It does NOT instruct you to install “equipment” such as ADF, radio or whatever (this would be part of Part NCO)

According your suggestion, you design your aircraft to meet this requements, install that equipment required to become certified, and then you could remove all this equipement such as stall warning and fuel indicator as it is no longer needed???

Cobalt wrote:

Applying the certification rules to maintenance or ops is just silly. Sorry.

Fair enough if that is your idea on this. To get a new EASA ARC (Airworthiness Review Certificate) :

To satisfy the requirement for the airworthiness review of an aircraft referred to in point M.A.901, a full documented review of the aircraft records shall be carried out by the approved continuing airworthiness management organisation in order to be satisfied that: ………. 10. the aircraft complies with the latest revision of its type design approved by the Agency

So the type design (and thus the design basis as identified in the TCDS) stays part of the continued airworthiness requirements

CS-23 also gives an example MEL, with stall warning als mandatory for all operations.

FAA is not my expertise. Though it seems the same applies to FAA according FAR 43.13B, see this Inspection Authorization Information Guide

The holder of an IA must personally perform the inspection. The regulations do not provide for delegation of this responsibility. Approving major repairs and major alterations is a serious responsibility. The approval action should consist of a detailed investigation to establish at least that:
1. All replacement parts installed conform to approved design and/or have traceability to the original equipment manufacturer (OEM).
2. As installed, the installation conforms to approved data that is applicable to the installation.
3. Workmanship meets the requirements of 14 CFR part 43, § 43.13 (the aircraft or product is equal to its original or properly altered condition).
4. The data used is appropriate to the aircraft certification rule (CAR 3, 14 CFR part 23, etc.).
5. Work is complete and compatible with other structures or systems.

So the (initial) certification rules are not only applicable to the intial design, they also stay part of the continued airworthiness procedures, both under FAA and EASA. The stall warning is part of Part 23 as well, so I doubt you can legally fly without the stall warning on an N reg as well. It does no longer conform to the orginal condition.

If you kill yourself in a PA-28 in a stall/spin accident just because the stallwarning is INOP … you will kill yourself anyway.

Cobalt, that is a very good explanation, and written clearly in that fashion it is interesting to read. God knows what EASA would make of a certified aircraft like mine that not only has no MEL, it also has no officially approved Pilot Operating Handbook. For the purpose of this discussion all that’s fine however, because it also has no stall warner!