Where might your IFR application go wrong?

There are a number of factors that aircraft owners and builders should consider, that can cause delays to a Night/IFR application.

Electrical system single points of failure. The most common issue that has to be rectified before an aircraft can be considered for an IFR clearance, with the dreaded Avionics Master-switch as the prime culprit. The idea of a single switch to turn on all the avionics might look like a good idea until the day when the switch converts itself into a collection of small plastic and metal bits in the footwell. The outcome is much the same as turning the avionics switch off, potentially no radios nor navigation equipment. It’s easy to design this problem out, but you would be surprised how often this single point of failure is seen.

Multiple pieces of required avionics equipment wired to a single circuit breaker comes a close second. Deferred defects. Some owners (and Inspectors) seem remarkably tolerant of deferred defects, shifting rectification of known, but ‘non-critical’, problems to some point in the future. While this might just be acceptable for VFR aircraft, the increased reliability requirements for IFR flying preclude this approach. Obtaining an IFR approval often involves resolving a number of issues that could, and perhaps should, have been dealt with previously.

Battery capacity. IFR flying requires that all the essential electrically powered systems need to keep working for at least 30 minutes in the event of an alternator failure. The calculation is slightly complicated, such that the IFR Assessors tend to look for 45 minutes safe operation using a simplified method.

With modern, individually battery backedup EFIS systems, this is almost trivial to achieve, but older systems with power-hungry equipment might struggle. Garmin GNS series navigators are but one known power-hog… Placards and lighting. Most owners who have built their own aircraft can pretty much operate the switches and controls with their eyes shut. But what about the next owner when the aeroplane is sold? Or a group-operated aircraft? CS-23 says the aircraft shall be capable of operation by an average pilot without special skill or knowledge.

Put a blanket over the cockpit and decide if you could undertake immediate actions in the event of any particular emergency, based only on the placards and lighting fitted. If not, changes will be required.

Birds-nest wiring. The standard of electrical installation in Permit aircraft is spread over a wide spectrum. We can only speculate if some of it is really suitable for VFR flying, but the demands of IFR require a high level of reliability and thus a higher build standard.

Cabling needs to be of an appropriate type (aviationgrade wire) installed in such a way as it cannot chafe or get damaged by control runs, baggage or passengers. Pitot-static faults. In deference to the more critical requirements for the pitot-static systems when flying IFR, a physical validation of the pitot-static system using calibrated test-equipment is required.

Leaks are sadly, surprisingly common (and often very difficult to track down).

Issues with static-ports often give rise to off-limits ASI calibrations.

Complex centralised electronic circuit breakers. Systems such as VPX are popular in some quarters. They also introduce a potential single point of failure that could take down all electrical systems in a single hit.

There is no prohibition on the use of such systems, but, where they are fitted, the owner will need to show that the failure of the power distribution system will not produce an adverse outcome in terms of flight in IMC. It may be that individual instruments are provided with stand-alone battery backup, or that an emergency-power bus is provided to power the essentials if the power distribution system should fail.

Electric trim. There are a whole host of bad things that can happen to electric trim systems, not all of these easily mitigatable. Flying IFR, or at night, out of trim is not fun so this needs to be thought about.

Trim runaway is the obvious issue, but what about a motor failure in the trim servo? This is hard to resolve and there is no requirement under CS-23 for duplicate systems.

The emergency checklist in the POH will need to provide guidance.

Document control. The document pack, used for IFR approval, forms an integral part of the Permit to fly in IFR. As such, it’s necessary to have proper document control with dates, issue numbers and a record of changes incorporated into each document.

It goes without saying that everything must be appropriately signed and that any modifications will need to be processed in the normal way.

Above Placards are one of the most common causes of issues with Permit IFR applications. These are good clear examples.

Above right While installing avionics is a big part of the job, configuration and testing is also vitally important.

01 If your wiring looks like this, the aircraft might not be a good candidate for IFR or night approval.

02 Take care that upgrades and repairs don’t cause issues. Swarf is the single biggest enemy of electrical wiring, so protect existing equipment if working in situ.

03 The required testing of all avionics needs some expensive equipment, and you’ll almost certainly need to engage the services of a Licensed engineer.

04 A new wiring loom ready for installation.

05 Thought must be given to the design of the aircraft’s electrical system, and how backup power is provided.

Someone new to the aircraft comes with fresh eyes and a clear remit. The test-card includes checks on control response, ergonomics, instrumentation and systems. It needs to be flown by an experienced and current IFR qualified pilot, ideally with experience on type.

Such is the breadth of experience of the LAA membership, an experienced commercial pilot, fast-jet pilot or flying instructor, also with time on pretty much any LAA type is never far away. The test flight is almost always flown with the owner / builder as the observer, and without exception they have always admitted (if sometimes reluctantly) that it was a very valuable learning experience.

Evidence gathered in defence of the IMC (now the IR(R)) some years ago, showed a clear safety benefit gained from private pilots holding an instrument rating. With the opportunity now available to LAA pilots to fly their own aircraft in IMC, if only to undertake training, maintain currency and revalidate, the time is right for more of the LAA fleet to become IFR approved.

The (now not so) new LAA Engineering Director, John Ratcliffe, is aware of historical issues with lack of continuity and delays in the IFR approval process, and has prioritised improvements. Given the likely increase of applications following the publication of this piece, there is also a high likelihood the current complement of IFR Assessors may prove inadequate for the task. The LAA would be interested in talking with suitably qualified individuals who might be interested in boosting the numbers.

Night flying

While it is possible to gain a night approval without IFR, the requirements for night flying follow closely from the IFR approval. In most instances, aircraft have been cleared for both in a single process.

Clearly the main additional requirement for night flying is lighting, both internal and external. This can be approved via a simple check by an IFR-approved Inspector.

The night test flight is not so simple as it requires flying the aircraft outside its initial permit limitations. Before the night test can be completed, an additional flight test authorisation must be issued by LAA HQ and agreement sought from the airfield operator confirming that they’re aware of the mildly increased risks involved with flying under test conditions.

IFR Inspectors

Taking account of the added requirements for IFR flight, the LAA has designated a subset of the Inspector community to act as IFR Inspectors. These are listed on the LAA website. Aircraft flying under IFR and night privileges will require both the initial documentation and continuing inspections to be completed by an IFRqualified Inspector.

LAA Technical Leaflets

Process guidance advice

tinyurl.com/PermitIFRprocess

Assessment of aircraft suitability

tinyurl.com/PermitaircraftIFRassessment

Peter Bentley is one of the LAA’s IFR and Night Assessors, guiding owners through the process of gaining IFR and night approval. Peter is a Luscombe owner, restorer and pilot who runs Aeroplane Electrical near Winchester, offering a full electrical service for Permit and Vintage aircraft owners. ■