This is a reminder to organisations- AOC/CAT-Operators, Part M/CAMO and associated Maintenance, Business/Corporate Operations, Rotorcraft, General Aviation and State Aircraft. Also applicable to Leasing organisations.
For additional information on General Aviation flights for maintenance checks, ferry and engine health under COVID-19, please see the guidance on this page, directly below this section.
This general notification covers- Engines and APU'S, Operation during preservation/storage, Fuel and Biocides, Rotorcraft transmissions.
As a result of the current Covid-19 situation, many aircraft are being taken out of service on an unplanned basis and undergoing preservation. While larger organisations will have established procedures, this will need to be addressed by organisations for whom this is not a normal aspect of their business. In addition, the numbers of aircraft involved can produce a challenge in terms of availability of the specified preservation equipment and processes
This notification seeks to assist organisations, particularly those unfamiliar with the storage and preservation of aircraft, by reminding them of the appropriate measures and sources of information available, so that when aircraft are returned to operational service they can do so with a minimum of additional disruption whilst maintaining an appropriate level of safety.
General
Organisations involved in operation, maintenance and maintenance management of stored/parked aircraft are reminded that they are, as a minimum, required to follow the aircraft type certificate holder recommendations for correct preservation methodologies identified via the Aircraft Maintenance Manual (AMM) and/or the Engine Maintenance Manual (EMM).
Engines should be protected and preserved from contamination and deterioration, as a failure to strictly follow TC holder instructions could result in deterioration of internal engine components such as mainline Bearings, Compressor and Turbine components and associated systems such as Engine Controls, Electrical, Fuel, Oil and Hydraulic Systems. In addition Rotorcraft drivetrain and rotating dynamic components will also need to be considered.
Where it is not possible to follow the TC holder AMM/EMM instructions because of the current circumstances, for example lack of availability of equipment then application should be made to the appropriate Type Certificate holder for acceptable alternative instructions.
Some TC Holders have already issued specific communications to operators, CAMO organisation and Maintenance organisations regarding approval of alternative methods as a result of the COVID-19 restrictions. When TC holder deviations are granted, the CAMO and the Maintenance Organisation must maintain adequate records of the approval of the deviations. The workpack and any release documents must refer to the TC holder deviation in order to demonstrate that the aircraft has been maintained appropriately at the point of reinstatement of any flying activities, and it should be ensured that that all non-standard equipment or materials have been fully removed before the aircraft/engine is operated to avoid damage or inflight issues.
Auxiliary Power Units (APU)
For aircraft equipped with auxiliary units, similar consideration should be included when preservation and storage periods are considered.
Blanking of intake and exhaust
Engines and APUs can quickly deteriorate if, as a minimum, the correct blanking to the Intake and Exhaust is not properly installed and checked and maintained. This is the first line of defence to protect and preserve engine(s) against potentially damaging ingress of FOD which may cause unforeseen airworthiness issues.
Experience has shown that birds also cause unexpected obstruction resulting in potential damage which could have been prevented by effective blanking.
Some Type Certificate Holders/manufacturers may authorise, via special technical requests, approval of non-standard engine protection/blanking equipment if the OEM approved items cannot be obtained quickly.
As mentioned above, adequate records of the acceptance of these alternatives must be retained.
Environmental conditions
Reference must be made to the Type Certificate Holders/manufacturers maintenance recommendations (AMM, EMM) for storage in differing environmental conditions.
Storage and preservation in conditions of elevated humidity, particularly if adjacent to saline environments i.e. coastal airfields, should be additionally considered for the effects on the engine internal air passages and electrical connections, whereby corrosion etc. may be exacerbated. Compressor linings may typically be at risk of deterioration during such periods.
Correct blanking of intake and exhaust provides mitigation against such conditions.
Corrosion Inhibiting- may be necessary, depending on the length of time the engine may be required to be in preservation and non-operation.
Dessicant materials- may also be required to be utilised. Refer to the Type Certificate holders/manufacturers recommendations. Inspection/checks at a recommended period for such moisture mitigation may be required to prevent unnecessary moisture build-up and deterioration of the dessicant.
Windmilling- in some instances, depending on exposure of the aircraft to wind direction and gusting while parked and because of the design configuration of the particular oil system and bearing lubrication, it may be necessary to prevent rotation of compressor and turbine rotor assemblies. The Type Certificate Holder/ manufacturers maintenance recommendations (AMM, EMM) for windmilling mitigation techniques should be consulted.
Operations during the preservation period
All aircraft manufacturers provide and publish instructions for both short and long periods of preservation of installed engines. The Operator/CAMO and maintenance organisation are strongly advised to adhere to the relevant instructions and preservation methodologies, which may include the following:
- Dry cranking
- Ground starting and running for short periods at idle
- Ground starting and high-power running
The above starting and running being undertaken in various combinations such as weekly/monthly or longer schedules will be particularly important if the aircraft/engine is expected to be placed back into service quickly.
Close inspection should be accomplished of the intake, bypass, exhaust and any other ductwork or aperture, drain line/masts, access doors, etc. prior to the above activity for potential blockage and obstruction that could cause avoidable damage to the engine. In addition, fuel/hydraulic system leaks due to unforeseen seal and pipe connection/interface deterioration may have taken place during the storage period.
Organisations should be aware that over-fuelling and potential pooling of flammable liquids may provide sources of ignition and fire on initial start-up i.e. hung starts.
Note- in certain instances, if the airfield where the aircraft is stored is non-operational, then ground starting and running may not be permitted for safety reasons due to suspension of airfield fire services.
In this case a dry crank may be the only option if permitted on the specific engine type. Consultation with the CAMO, the maintenance organisation and/or the TC Holder in such circumstances is strongly advised.
Fuels and biocides
The Operator/CAMO should build into their storage programme some microbiological testing of the fuel as any water left in the fuel will settle, allowing the growth of micro-organisms (bacteria, moulds, yeasts) in water boundary layer and feed off the hydrocarbons in the fuel. Good housekeeping is the first measure to prevent water accumulation in the fuel tanks with regular water drain checks.
In the case where microbiological contamination is detected and needs to be treated with biocides, all maintenance personnel, aircraft owners and operators are expected to follow current/latest instructions from the aircraft / engine TC holder.
Any application of a Biocide into the fuel system of an aircraft must be carried out in accordance with the Type Certificate Holder's instructions and great care must be taken to ensure the correct amount is administered to the fuel. Many TC holders mandate the use of a metering rig to control the biocide application.
Where biocide usage is approved for airframe application only, the engine(s) should not be operated with fuel containing biocide and the aircraft TC (STC) holder is to provide appropriate maintenance procedures to prevent ingestion by the engine of fuel containing biocide.
In response to EASA SIB 2020-06 and the “All Operator” message published by Dupont removing KATHON FP 1.5 from aviation use, CAA has been working in partnership with the Health and Safety Executive to obtain the necessary permissions allowing the import of BIOBOR JF as an alternative Biocide for operators to use.
The CAA has been advised that temporary permit number UKCSP-2020-02 has now been issued for 180 days allowing the import of BIOBOR JF into the UK. This permit will remain in force until 27th October 2020, with work continuing to try and secure an extension. This communication will be updated if an extension is secured.
Organisations are advised that in line with the permit requirements, orders of BIOBOR JF have to be made through Aviall - organisations can place an order directly with Aviall if they already have an established account. Contact details are provided below for information.
Aviall can be contacted at:
Email - europe@aviall.com
Tel - 31-252-245-900
Aviall also have a sister division, Boeing distribution services, contact:
Email - timm.boehmcker@boeingdistribution.com
Please be aware that the CAA cannot enter into correspondence regarding the conditions for the permit.
As a mitigation in the interim period the Operator/CAMO/maintenance organisation should consider the following as best practice while their respective aircraft are in the stored/parked conditions:
- Carry out regular fuel / water drain checks
- Carry out Microbiological contamination testing
- Follow Type Certificate Holders Recommendations for the application of a biocide
- Operators / maintenance organisations should have robust training / procedures for engineers adding biocide to an aircraft and introduce a second check were possible before the application commences to minimise any chance of exceeding the maximum dose.
- For each application of an approved biocide additive, record the following information:
- i. Type of biocide used
- ii. Quantity of fuel in the aircraft tank before additive injection
- iii. Quantity of fuel uplifted into the tank when injecting the biocide additive
- iv. Quantity of fuel in the tank after injection of the biocide additive
- v. Quantity of biocide additive injected for each application
Rotorcraft Transmissions
Where the Aircraft is non-operational for extended periods the impact of environment and storage conditions on the rotorcraft drivetrain and rotating dynamic components must be considered. The Operator/CAMO should consult their contracted maintenance organisation or the Type Certificate Holder (TCH) with respect to any necessary maintenance to minimise the possibility of component deterioration.
Gearbox inhibiting, blanking and anti-corrosion techniques for exposed fescalised portions and areas of close tolerance movement such as damper pistons, mast, swashplate and bearings should be taken in to account when rotorcraft are inactive for the extended period. Main gear trains, if not appropriately preserved, may lead to the instigation of unnecessary corrosion, which while initially may not be realised on restarting operations, may subsequently lead to early removal or component failure in later service.
Appropriate maintenance work orders detailing work carried out and the need for recovery action post storage will be required to demonstrate TCH instructions have been complied with.
Mitigation of the above may be addressed by regular starting and running, however in all cases the Operator/CAMO should follow the recommendations of the applicable aircraft and engine TCH using their published approved data, such as the Aircraft Maintenance Manual or Service Bulletins. In the absence of such data the Operator/CAMO should contact the aircraft /engine TCH directly for advice.