Certified, Approved and STC systems

The absolute key instrument for IFR flight is the attitude indicator. For an individual aircraft to obtain approval, it will need both a primary attitude indicator and a back-up. Historically the AI would be vacuum-powered with an electrically powered turncoordinator as backup. Increasingly we are moving to multiple electronic instruments and the reliability of these need to be assured. Initially the LAA was concerned about common mode failures and insisted that the primary and backup instruments were from a different manufacturer, but the advent of STC approved systems has greatly alleviated this concern.

Even in the CoA world there is some confusion about STCs, PMAs and a whole host of other alphabet-soup approval standards. We’ll not get too involved in that here, but suffice to say that any flight instruments that are either approved as part of an STC or very close cousins to STC approved kit will be accepted by the LAA.

A good example would be the Garmin G5, where both STC’d and non-STC’d versions are available. In practice it’s the same hardware (possibly with slightly different software) from a major corporation. You can install it without further approval in a CoA aircraft and it would be unreasonable for the LAA not to accept such equipment.

Where complex (glass) attitude instruments are not STC’d they will need to be on the LAA approved list, with primary and backup AI from different manufacturers. There are no stipulations about traditional single-function instruments, either electric or vacuum powered.

Similarly, ensuring continuity of power for primary and backup instruments, especially if they were both electrically powered-required, historically required very careful checks of both electrical loads and battery capacity. Anyone who has completed an instrument rating will be familiar with the concept of load-shedding to ensure sufficient endurance from the battery to return safely to Earth in the event of an alternator failure.

While the requirement for load and capacity checking has not gone away, the advent of individual backup batteries for each instrument massively increases reliability and the consequences of the loss of all power after an alternator failure are enormously reduced.

important, the first step in the approval process is to assess the suitability of a given type via a first-of-type (FOT) test. This needs to be flown by a qualified professional test pilot approved by the LAA. The test pilot will be looking at a type’s suitability for IFR flight, including stability, manoeuvrability, ergonomics and ground handling – among many other things. Following this FOT test flight it may be that specific limitations are imposed for a particular type. Typically, these might include reduced aft CG limits (to enhance longitudinal and yaw stability) or in some cases aerodynamic changes to reduce (or increase) control forces. The good news for the majority of owners looking at IFR and night approval is that the majority of the LAA fleet likely to be suitable for IFR have already been type-approved. There will shortly be a Permit IFR page on the LAA website where this information will be available. Types not already approved will need one-off testing.

Assuming the aircraft is type approved, the next step is to look at the individual aircraft design and specification. For Permit IFR approval the configuration of the aircraft must be better defined than for a standard VFR clearance. That is done by creating an aircraft equipment list. All essential items on the equipment list will be required operative for an IFR departure. The good news, as noted above, is that individual owners don’t have to swat-up on the contents of CS-23 or the ANO as the LAA team have condensed the required information down to a couple of forms.

IFR Assessor

All this information is gathered together and used to complete an LAA Mod 15, which is a coarse filter that will hopefully weed out any unsuitable aircraft with little chance of acceptance and save the LAA and their owner’s unnecessary work. Once the Mod 15 has been accepted, you will be allocated an IFR Assessor. Your Assessor will guide you through the process of working through TL2.28 and supplying the accompanying documentation (see sidebar on page 21).

Once all the required paperwork has been created, it’s time for a test flight. The IFR element of the flight test can be conducted in VFR and as such needs no special permission. As with all simulated IFR flight, an observer will be required to keep a lookout while the test pilot gets on and does their stuff.

LAA members often question why they can’t do the test flight themselves? Surely, they are best qualified to fly their own wonderful creation. And therein lies the problem. The owner and builder all too often become accustomed to the idiosyncrasies of their own aircraft and see past deferred defects and overlooked issues.