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Flight Recorder FAQ

Frequently Asked Questions about the CIMA standard for flight recorders

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What is the standard all about?

For years people were talking about using "GPS Loggers" in microlight championships, but suitable equipment only became available at the right price in mid 2002 to make this a genuinely practical proposition.

This is quite complex technology, to avoid a myriad of different and incompatible data formats, units, map datums, time-bases etc. which would make their use, especially in championships, a difficult and unreliable business we had to come to an agreement about some sort of specification or standard.

As it happens, the International Gliding Commission (IGC) has a well developed and extremely detailed standard which has been extensively proven in gliding championships and records since it was created in 1995 so it was not necessary to invent something completely new.

A document based on the IGC standard but adapted to our unique demands was presented to the November 2002 CIMA meeting with the view to it being incorporated into Section 10 as a new Annex 6. The meeting accepted the document and it is now incorporated in the FAI Sporting code for microlights and paramotors as Annex 6 "GNSS Flight recorders".

  • S 10, Annex 6 describes the different kinds of GPS receiver/recorders which can be used to provide valid flight evidence in Microlight championships and records.
  • It describes the terms of reference for a CIMA sub-committee; the Flight Recorder Approval Committee (FRAC) and describes the sort of work it should do.
  • It describes the hardware and software requirements for CIMA approved Flight recorders (FR's) which may be used in some records and are the only ones which may be used in championships.

Why do we need a standard at all?

People were using IGC approved Global Navigation Sattellite System (GNSS) FR's in microlight record claims for some years. The fact is though that this was never approved in any detail by CIMA and this document helps to resolve some of the problems associated with using them.

The primary need for this standard however is in championships where flight recorders help solve the perennial and expensive problems associated with marshalling and scoring big microlight championships.

Benefits include:

  • Better tasks: Common complaints about tasks include "they are all the same" or "they favour expensive aircraft over pilot skill". Tasks using FR evidence have the potential to be much more diverse and more oriented towards pilot skill.
  • More accurate tasks: No more marshals taking wrong times, markers being placed in the wrong location, aircraft "not" flying through gates Etc. Flight recorder time is absolutely accurate and positional information is very accurate.
  • Less cheating: Because FR's record a pilot's every move, all those rumours about pilots doing things they shouldn't have simply can't happen. Of course the introduction of FR's will introduce some completely new problems but the proposed standard attempts to deal with them.

Why can't I use the recording facility of the GPS I already own?

The CIMA standard allows most ordinary GPS's to be used as a source of evidence for records.

In championships, approved flight recorders must be used because the crew must not have access to any GPS flight information. If they did, then the whole thing would very soon become so easy that we may as well abandon traditional championships altogether and stay at home and do them on flight simulators connected to the Internet.

Sometimes when there are not enough approved FR's to go round, other types can be 'sealed' into a bag but this is a very unsatisfactory solution as the pilot has no idea it is even switched on and without the specialist software of approved FR's which streamlines the data transfer, getting the information out of them is time-consuming and error-prone.

There are other good reasons too:

  • Some don't record GPS altitude, which is an essential requirement.
  • Pilots can't operate the PEV "mark" button.
  • Fix intervals of longer than 5 seconds is no good in championships. Many of them can do 5 second fixes, but do not have enough memory for longer flights and simply start overwriting the beginning of the flight.
  • Some only record fixes at distance rather than time intervals which is difficult to analyse.
  • Some of them have unknown and undesirable characteristics eg the "throw forward" effect. (Fly fast in a straight line, simultaneously cover the antenna and turn a sharp corner. Some GPS engines which are optimized for poor signals in urban driving situations will try to predict the route after the loss of signal and will throw forward the trace, eg into a turnpoint zone to which the pilot hasn't actually flown).

There is no reason why CIMA can't approve an "off the shelf" GPS which satisfied the standard and had some sort of 'lock-out' feature which could be set by the organization to prevent the pilot from getting any flight information during a championships but which otherwise could be used as a normal receiver. Detailed conditions of use would simply be included in the approval document.

Why do we need such detail in the specification?

Compared to the comparable IGC document, S10, annex 6 is quite short! The fact is that it addresses some quite complex technical issues and the specification needs to be fully and properly defined or a championship organizer gets into trouble downloading and analysing the thousands of tracks he will collect at a typical international championship.

What does the specification mean?
First, it defines three types of FR.

  • Type 1 FR's are the only ones CIMA (via FRAC) approves. They must not display any flight information. They all have an approval documentdescribing their use and limitations in Microlight championships and records. They are primarily for use in championships but can also be used in speed or distance records which don't require accurate altitude information to be recorded. They must be capable of recording fix information at a rate of better or equal to one every five seconds which must include time, position and GPS altitude. They must also be capable of recording the time and position of pilot "mark" button events (PEV's).
  • Type 2 FR's may be used in any record claim. At present these are only FR's approved by IGC for use in glider World record claims and in addition to the information recorded by type 1's they record barometric altitude, have a secure method of data transfer and in "engine off" records have Means Of Propulsion (MOP) recording. They must be used in accordance with their IGC approval document.
  • Type 3 FR's include GAC approved FR's and any "off the shelf" GPS units which are capable of recording GPS altitude. When operated according to certain conditions laid down in the standard, the data may be used as evidence in speed and distance records.

Second, it defines the exact format the data must be in when it is transferred from FR to PC. The primary objective here is to get the data out of the FR and into a PC as quickly and reliably as possible in a common data-format using common units of measure, map datum, time-base Etc. The IGC format for FR data is readable by many different flight analysis programs. To ensure consistent auditable data the standard defines exactly the "mandatory data sub-set" required for Type 1 approval within the IGC format.

Third, it describes the system and method of approval of FR's to CIMA Type 1 standard and the sort of testing which should be done.

How reliable are they - really?

IGC have been using GNSS flight recorders with considerable success in championships and records since 1995. GAC have been using them in championships since early 2001.

The first time FR's were used as the 'primary' source of pilot performance in a World championships was at WMC 2003 in UK. An analysis after the event suggested the FR's used were better than 95% reliable and nearly all errors were 'pilot induced'; either the FR was incorrect positioned in the aircraft so the antenna was getting a restricted view of the sky, or pilots were forgetting to switch them on.

Flight recorders have been used as 'primary' in every major microlight and paramotor championships since then. Most errors since then have been caused by the organizer not getting correct physical fixes of the points used in scoring. These are usually fixable during the event, though it usually causes considerable delays to the final scoring.

Who will buy these flight recorders?

All pilots who wish to compete in competitions will have to have one. Whether it is bought or hired is their, or their team's choice. It is not practical or desirable for a championship organizer to provide them and in any case the cost would simply be passed on in the form of an increased entry fee.

More importantly, pilots need to practice with them so they are confident of their own FR's capabilities and limitations in their own aircraft, for example, it is quite easy to obscure the antenna, especially in a paramotor. The style in which tasks are flown will also be slightly different which will also need practice (eg reliably being able to hit a 200m radius cylindrical scoring zone). Ultimately they are very much for each pilot's benefit, they are not an unnecessary 'imposition' and they need not be expensive.

How are pilots scored in championships?

A scoring zone will normally be a cylinder of 200m radius and of infinite height. To score, a recorded fix point must either be within this circle or the line connecting two sequential track fixes must pass through the circle. Additionally the task may require one of these fixes to be associated with a PEV "mark".

A Start line, IP or gate time is taken from the fix immediately before the line is crossed. A Finish line or FP time is taken from the fix immediately after the line is crossed. For many reasons it is impractical to deduce the exact time a FR crosses a timing gate from the two adjacent fixes, it is therefore to the pilot's advantage to have a FR which records frequent fixes; ideally 1 each second.

What problems can arise in championships?

It is vital for the task designer to understand - and it seems to be a difficult concept for some people to grasp - that with FR's you are using two maps which are not necessarily the same.

One map is the printed map the pilot uses.

The other is the "GPS map" which is projected onto the surface of the earth by some satellites which the scoring system uses.

The important thing is to reconcile the two in all cases where scoring is involved, it is not good enough to have a "calibrated" map like you can do quite accurately with Oziexplorer because it still does not account for the unknown number of "artistic" differences between the printed map and the GPS map, and ALL maps have artistic differences.

It is not so difficult to do however - the Director can plan the task on the printed map but the key is that he MUST visit every point which involves scoring by land or air and get the true GPS coordinate fix. It does not matter whether it is a turnpoint, a hidden gate, a marker or a secret photo, he must have a true fix. Getting coordinates off the printed map and putting them in the GPS mapping system does NOT reconcile the two maps; this has been demonstrated a number of times by lazy organizers.

The pilot flies with the printed map but the FR is recording off the GPS map. If the pilot passes the turnpoint correctly on the printed map, then, because the director has been there and got the GPS fix, he knows the pilot has been there on the GPS map even if there is an "artistic" displacement between the two when the two maps are overlayed. (This is very easy to demonstrate in Oziexplorer).

A good example: Draw a straight line on the printed map which goes from a known point, through a known point, to a third known point, eg road junctions all maybe 20 Km apart. Go to those points, get the GPS coordinates and plot them mathematically into Oziexplorer or something like it. It is almost guaranteed that the mathematically plotted line through the three points using the GPS coordinates will not be exactly a straight line - but if you think about it, it doesn't matter, because all you are interested in is the points and all the pilot is interested in is flying the straight line on the map.

The problem becomes more complex when you start scoring declared average speeds Etc. but if you always think through the problem on the basis that the "two maps" must always be reconciled, then there is always a solution.

There are various other problems specific to FR's:

  • The organization must be sure that each FR is in each machine so they must either be sealed to the machine or the serial number must be checked immediately before takeoff and after landing.
  • It is not easy to deduce precise takeoff or landing times from FR data. Instead a timing gate should be used, positioned at or just beyond the end of the deck. It must be arranged such that aircraft cannot taxi through it a second time before or after the task!

What analysis software is available?

MicroFlap is the best one as it was designed from the ground up to provide the sort of analysis we need in microlight and paramotor championships, but the initial learning curve is quite steep. There is nothing yet which is truly "data in - scores out" which is the ultimate ideal, but otherwise there is a load of software out there which reads .IGC format files.

The future...

FR's make championships fairer to compete in and easier to run than the previously used 'traditional' methods of pilot photos and observations by marshals, it is however quite a lot more 'technical' for the organizers and they frequently struggle, but this can be completely solved by adequate preparation. In larger competitions with hundreds of FR's there is still a major bottleneck in the download and analysis of all the data. This could be speeded up using the new generation of FR's capable of transmitting the data by GPRS or Satellite communication systems which would get the data back to HQ before the pilot. If the analysis software was improved so it was genuinely "data in - scores out" then we really would have the possibility of instant scoring...

Added by José Luis Esteban Last edited by José Luis Esteban on 29 Nov, 2009 19:25. Quick links: or Flight Recorder FAQ
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