PROCEDURES
Airline preparedness to perform Functional Check Flights
Once it is acknowledged that FCF deserve special treatment, setting up all that is needed at the airline level to be prepared for performing such flights encompasses a number of aspects that are reviewed hereafter.
Selected and trained crews
There are certain characteristics of individuals’ profiles that are more important in check flight work than in other tasks. In the airlines, most young pilots are selected against criteria with a different objective in mind. However, check flights are a fact of life for all airlines and often the task falls to the Chief Pilot or other senior personnel like the fleet captain, or the fleet technical pilot who may see such flights as a chance to get “out of the office”. Not all these categories of people, important as they are, may necessarily be best suited for the task nor do they necessarily have the available time to prepare in the way they should and probably would wish to. So what should be looked for in a pilot or engineer who will be recruited into the “checking community”?
There are 4 pillars on which a check crew member builds a successful career. These are Knowledge, Skill, Aptitude and Experience. “Not much difference there from my world” one may rightly say but let us look at some of these characteristics more closely in a “checking” sense.
Knowledge
A deep knowledge is clearly required of the aircraft, the theory behind the task and the role. A determined inquisitive mind is essential if one is to survive in the check flight world, and one would expect all check aircrew to be asking questions and then more questions until they receive an answer that is both “right” and makes sense. Questions coming from newcomers are especially welcome, as they keep the organisation true and sharp. Disinformation is generally easy to recognise and has no time in the checking world, so the answers had better be good.
An answer that was right 5 years ago may not be right today. Circumstances change and those changes sometimes demand a re-think. Equally, it is important to be self-reliant in this regard. Don’t wait for the information to come to you, go looking for it and develop good contacts and sources of quality information.
Skills
Valued skills include Observation, Interpretation, Analysis and by no means least, Communication. So called “motor function” flying skills for the pilots need to be pretty good too but it may be surprising to some that pure flying coordination and technique is not necessarily the top priority as long as this aspect is to an acceptable level for the task. However, flying ability does have an impact on the capacity of the pilot to handle high workload situations and therefore it will be referred to later in the section about Upsets.
Some of these skills do not come naturally to some.
It is necessary to think through each check point or task and decide which parameters are important. Know also when and how often to read them and then when to record them. For the third crew member in this situation this recording task is always secondary to acting as the safety “observer”, someone with an immediate oversight of the way each of the check points is being conducted and someone who can therefore issue timely warnings.
Aptitude
Aptitude is a bit more complex. In this context, it refers to whether someone “thinks in the right way” and demonstrates the right judgement.
Firstly, check trainees need to be able to handle several apparent paradoxes. Let us take an example or two. Take the issue of when a check crew member has to stand their ground on a given topic versus when they can afford to be flexible. If we take a situation where an aircraft may need some re-work before or after a check flight but is due on the programme later in the day, you can immediately see the pressure that has to be handled in this fairly common situation and knowing when it is ok to be flexible or when a tougher stance has to be taken is part of the job.
Taking another example, in a typical group discussion about, for example, a specific systems check, certain people will inevitably have more knowledge than others, so the issue of when to speak from within your own knowledge and when to listen becomes a skill and a challenge. With the right level of sensitivity and awareness of each other, the team dynamic has to lead to the right answer.
Perhaps the most well-known is the issue of confidence. A check crew member has to have sufficient self-confidence to make decisions when necessary and to intervene in developing situations but not so much confidence that may lead to check points being flown in conditions outside the safe limits. There are many such paradoxical situations to be faced and correctly resolved in the world of check flights. Good team members get more of these situations right than wrong.
The right type of pilot or engineer should therefore be naturally skilled at Crew Resource Management and be especially good at listening. But check flight CRM is very different from the normal airline route situation. A ground engineer who is acting as a Functional Flight Check Engineer may well be the person with the best knowledge of a particular system. The second pilot likewise may be a specialist on a given area so the classic cockpit leadership balance may change during a check flight and should only tip with certainty towards the Captain when and if a final safety decision has to be made. Clearly, in the normal airline situation, the authority gradient is clearly defined. But each airline will need to decide how to handle the authority gradient issue in the context of their local and national culture. The trick is to ensure on check flights that all those with knowledge and useful information are really heard, whatever their level, number of rings on their jacket, nationality, gender or salary grade. Check pilots in particular, also need to be able to achieve a good balance in their activities and maintain the necessary level of self-confidence without an over developed ego. Look for people who are not trying to prove how good they are but rather how good (or bad) the aircraft is. Interestingly, this trait is also critically important in the flight display world.
In some respects this is the key difference between the checking world and the normal operational pilot world. Younger pilots spend their developing career improving their skills as a pilot and having to demonstrate those skills under test conditions. If the flight doesn’t go too well the normal reaction is, “it must be me”. “I am having an off day”. In other words they look inwards at their own performance. The checking world is different. It demands that they become “the standard” and that they use that standard to assess the aircraft they are flying. It is the aircraft that is under examination, not the pilot. They have to look outwards. If the same type of aircraft was flown yesterday and its response through a given manoeuvre was “normal” but today it is not or it feels different, then what has changed? Has something altered? Is the weight and Centre of Gravity (CG) the same, or is it potentially something even more serious like a degraded flight control system due to something like trim damage?
Finally, and highest on the list of desirable characteristics, is personal integrity which is valued above everything else. The check flight specialists need to be people mentally strong enough to take responsibility for their decisions (good and bad) and then be able to live with their mistakes, learn from them and communicate them to others. Hours can be wasted chasing a non-snag or flight characteristic when in fact the culprit was the pilot who had selected the wrong configuration or moved the wrong switch at the wrong time. In the development test world there is no hiding place as everything done is filmed, instrumented, telemetered and examined by teams of specialists but this is not true of the airline check flight situation where good old fashioned integrity is vital. There is no more important characteristic in this activity.
Experience
Experience (of the right kind) is extremely valuable in terms of improving judgement, prioritisation of task and risk evaluation but experience can also be a great deceiver. There are many 35,000 hr airline guys, in some parts of the world, who are totally unsuited to check flight tasks. Such people have much experience of doing repetitive and similar tasks rather than a range of different experiences against which to make good informed check flight judgements. So look beyond the hours and find out what relevant checking experience lies within the log book and how many non-routine operations have been successfully carried out by an individual.
Specific training
Identifying these main characteristics during an interview and selecting the “right” kind of person for this kind of work will buy you many dividends in the check flight scenario. Indeed, if you get the people wrong, no matter how good the process, it will still be at risk. Yet, training these people to further develop the knowledge, skills and attitudes to perform check flights is an additional asset.
It is quite possible to train check flight pilots inside an airline when the right expertise exists and is supported fully by management who recognise the need to get their people “up to speed” in a check flight sense. Some of the airlines with very large fleets, have a dedicated professional department whose role is to carry out the checks on all their fleet aircraft.
Equally, a manufacturers’ Functional Check Flight course has been developed by Airbus and has demonstrated very positive results. It is not designed to generate full test qualified crews but rather to give an initial immersion into the right type of thinking and to help airline check personnel get some way up the learning ladder and so prevent some basic errors. The course uses one of the Airbus aircraft types as a vehicle on which to hang the “generic” teaching elements and Airbus also uses this type to demonstrate the level of knowledge and skills that are needed to safely carry out FCFs.
Other aeronautical training agencies also do the same sort of thing but in a much more general way. The choice is with the airline.
THE AIRBUS TECHNICAL FLIGHT FAMILIARISATION COURSE
The analysis of actual Functional Check Flights that involved safety concerns allowed for highlighting some key aspects contributing to the safety of such flights:
- an aircraft checking mindset
- appropriate crew expectations
- specific skills to perform manoeuvres different from line operations
- recognition of the threat of differing objectives of crew members especially in an end of lease situation
- keeping away from a “tick the box” approach
- an awareness of performance and handling differences associated with unfamiliar airplane weights and CG
- new crew member skill sets and new knowledge
- a positive ATC interface
Based on this feedback from experience, Airbus developed in 2009 a Technical Familiarization Flight course with the objective to provide flight crew with Knowledge, Skills and Attitude to improve safety, quality and efficiency for conducting:
- Technical flights or Functional Check Flights (i.e. post maintenance, painting, etc.)
- Acceptance flights (i.e. handover between operators)
This course is designed for a crew of 3, 2 pilots and 1 engineer and is delivered by 2 instructors, 1 flight test pilot and 1 flight test engineer.
It combines a ground phase (2 days), a Full Flight Simulator phase (2 days) and a flight to cover all the aforementioned aspects to make FCF as safe as possible.
Guidance documentation
Beyond having the right people, being prepared for performing functional check flights also relies on an understanding of what these checks are, what they are for and how to perform them.
There has been a certain amount of confusion over the years about which document an airline should use if it is intending to carry out its own post maintenance FCFs.
Mistaking one manual for another could induce hidden risks that have no place in the world of Functional Check Flights. So which one should be used?
A Manual for each circumstance
A number of manuals have been developed by Airbus to perform “check” flights. Specifically, the ISATFM (In-Service Aircraft Technical Flight Manual), the PATM (Production Aircraft Test Manual) and the CAM (Customer Acceptance Manual).
There has been a certain amount of confusion over the years about which document an airline should use if it is intending to carry out its own post maintenance flight check.
The easiest, and incorrect, solution seems to be to use the one that is most likely in hand….the Customer Acceptance Manual, which has been received by all Customers during the acceptance flight of a newly delivered aircraft. However, this “solution” carries with it several hidden risks that have no place in the world of Technical Flight Checks. So which one should be used?
Although all the flights covered by these three manuals are meant to perform checks, each manual has a specific scope in terms of:
- The status of the aircraft (from straight off the production line to already in-service).
- The background of the pilots and the organization they belong to.
In a nutshell, these documents could be characterized as follows:
In other words, the only manual that is to be used to perform Functional Check Flights is the ISATFM. Do NOT use the CAM.
The ISATFM (In-Service Aircraft Technical Flight Manual)
As just mentioned, this is THE manual which must be used for In-Service aircraft. There is an ISATFM for each family of Airbus Aircraft: Wide Body for A300 family, Single Aisle for A320 family, Long Range for A330/A340 family, and Double Deck for the A380.
Each manual is divided into 3 parts:
Part 1 is the Ground Check phase
Part 2 is the Basic Flight Phase and
Part 3 is the Flight Phase with additional checks for Trained Crews.
These phases should be carried out in the logical and numbered sequence.
Here, we will deal only with the flight phases (Parts 2 and 3).
In 2014, the ISATFM flight phase was divided into 2 partsafter requests coming from the aircraft leasing community. It was recognised that the older generation of ISATFM manuals was quite complicated to fly for pilots who had no flight checking experience. The manual was therefore divided so that “Part 2”, became the basic function checks of the aircraft within the normal envelope, and “Part 3” the advanced checks to be performed by crews who had been suitably trained and therefore allowed a deeper technical check of the aircraft and its systems.
In fact, Part 2 is intended to be used for aircraft already in service, with no significant maintenance actions prior to flight, allowing a handover phase between operators. It could be flown by regular line pilots.
These are the primary reasons why Part 2 should not be used as a manual for carrying out Technical Flights within airlines.
The Part 3 flight profile is very similar to a production first flight, but without the checks for performance or degraded modes. At the end of the flight, the crew have a very good picture of the technical state of the aircraft.
In order to fly the “Part 3” flight profile, it is recommended that the crew should be correctly trained.
HOW TO GET THE ISATFM MANUAL AND USE IT?
The philosophy of use of the ISATFM document developed by Airbus is to support airlines in the development of their own FCF manual, adapted and customized to their own context of operation (airfields, checks, pilots profile…). In other words, the ISATFM has been designed as an “a la carte” menu, and is a guideline recommended by Airbus based on its expertise. But in order to support the safety of FCFs, each airline needs to go through its own thinking process and design its own manual based on this reference. This reflection may lead an airline to remove some checks if it does not feel confident about performing them or add some specific information considering its environment…
In order to make sure all airlines are aware of and acknowledge this required step, the ISATFM is supplied by Airbus upon request, after signature and reception of a legal waiver stating how to use this document. The legal waiver states that the airline should take control of its own document using the guidelines of the supplied ISATFM and that the reference to the document being an Airbus document should be removed and the Airline headings applied. Logically, it also states that the ISATFM document with Airbus headings should not be forwarded to third parties nor copied or stored, but this is only with the Airbus headings.
To receive the Waiver, airlines need to write (e-mail) to the secretariat of EVRT (evrt.control-room@airbus.com)
In turn, the airline will be supplied with the legal waiver which must be signed, and returned, in order to receive the document for their type of aircraft. The airline will then receive a pdf version of the document.
A FLAVOUR OF THE ISATFM… OR THE CHECKS TO BE PERFORMED IN FLIGHT
The first major actions on the aircraft in flight are the flight control check. After ensuring that all loose objects are secured and the weather radar is switched off, the pilot will pitch and roll the aircraft towards, but not exceeding, its protection limits – that is +30 to -15 degrees pitch with a pull of up to +2.0g and push to no less than +0.5g, and just over 45 degrees LH and RH. The objective is to ensure that the aircraft response and the “feel” of the aircraft is “normal” and that the envelope protections function as per design.
Following this, the autoflight systems will be checked with normal and stick over-ride disconnections, followed by a check of global speed protection that is carried out to monitor the control law reversions.
During the climb, the 3rd crew member monitors, and records, the systems parameters, whilst checking for abnormal values. The pilots keep busy performing Radio and Navigation qualitative checks. On arriving at FL310, the crew perform a series of checks for the engines, lateral trim (to check that the aircraft flies wings level) and anemometry checks of the altimeters, and angle of attack probes. Once happy, the crew will proceed with pressure checks. The first check is to inflate the cabin up to its maximum pressure limit in order to check the correct functioning of the cabin pressure safety valves. This check is critical as the crew must monitor very carefully that the valves open within the correct limits. Leak rate and depressurisation checks follow, which may take the cabin up to 14000ft cabin altitude, whilst checking the cabin leak rate (caused by passenger and cargo door seals), pack valve sealing, cabin altitude warnings and finally the dropping of the oxygen masks. This later check involves good communication and coordination with any cabin engineers on board. If there are “non-crew members” working in the cabin, a depressurisation to a lower cabin altitude may be advisable – in which case stopping the depress at the Hi Altitude warning (9550 or 11300 feet cabin altitude) then using Mask Man On, is a more prudent option.
After this, the crew will fly towards the operational ceiling of the aircraft, performing more anemometry checks to complete RVSM checks. At the ceiling, the APU will be started, and when stabilised, each engine generator will be selected OFF then ON, in turn, in order to check the correct transfer of electrical power to the APU generator.
The descent is relatively fast, with overspeed checks at MMO and VMO, plus speed brake deployments to check for any abnormal lateral behaviour. Wing and engine anti-ice are also checked in the descent, as is APU bleed at lower flight levels.
The descent is into an airspace known as “the block”. This is an altitude “block” agreed with Air Traffic Control normally FL100 to FL140 – but significantly depends on the geographical terrain where the aircraft is flying. If the terrain is high then a higher block altitude will be necessary! Here, the low speed checks are carried out provided that the aircraft has not acquired any ice in the descent. Prior to commencing any low speed checks, the Green Dot speed and AOA values are confirmed. If problems are found at this stage, then the remaining low speed checks may be abandoned. When the relevant values have been assessed and agreed, the aircraft will be decelerated in the clean configuration until it is stable at “alpha-max”. This condition is the stabilised minimum speed with full back stick using “normal law”. When the 3rd crew member has recorded the values, the pilot will perform the low speed recovery procedure and, immediately, the aircraft is set up for the alpha-lock test. This check is to confirm that, with a low speed / high angle of attack, if the slats are set from 1 to 0, they will not retract.
The aircraft will then be configured into the landing configuration and decelerated again to alpha max. It may be surprising to know that for A320s, A330s and A380s, the stabilised minimum speed will be roughly the same, in the region of 100 knots! Whilst both of these checks must be approached with caution and due care in terms of rate of speed reduction and gentle control use, provided the aircraft systems are working normally, they are relatively easy check points to fly.
The final checks in the low speed block, are to ensure that various systems are functioning correctly – Automatic Go-Around, Hydraulic locking of the spoilers (when hydraulic systems are degraded), emergency electric and Ram Air Turbine, and flap relief and audio warnings with various speeds and flap configurations.
The final check – depending on airfield capability – is an autoland. However this check needs to be carefully considered. Before checking the autoland system, the characteristics of any non Cat III ILS facility need to be assessed beforehand, preferably on another serviceable aircraft. (The readers may interpret that as meaning theyneed to fly another aircraft before they fly the check aircraft). The intended autoland also needs to be discussed with the local ATC as Cat 3 protection may need to be organised in advance.
It is important to note that the sequence of tests above has been carefully considered, is important and should be adhered to.
Why is it advisable to fly such a profile? The answer is that, while the ground checks performed by the hanger staff are very good and thorough, there may be still some aspects which the airline management feels cannot be adequately checked on the ground. The airline decision will be – “do we need to do a dedicated technical flight?”
Such decisions must be based on the local engineering and operational judgement on, the level and depth of overall maintenance that has taken place, the number of systems that have been disturbed, the applied modifications, the maintenance “history” of a given unserviceability and the significance or all these issues with regard to the flight control system, the engines, the aerodynamics and the sensors of the aircraft. The Aircraft Maintenance Manual reads as follows:
CONTRIBUTORS
Harry NELSON
Experimental Test Pilot
Simon PETERSON
Flight Test Engineer Instructor