ELECTRONIC FLIGHT BAG: ERRONEOUS PERFORMANCE INPUTS

ELECTRONIC FLIGHT BAG

home_pilot.jpg Electronic_Flight_Bag.jpg
Electronic Flight Bag Embedded from[http://www.navaero.com/images/home_pilot.jpg] on 21 September 2010 Electronic Flight Bag, Embedded from[http://www.boeingcapital.com/p2p/archive/09.2006/images/Electronic_Flight_Bag.jpg on 21 September 2010

PURPOSE OF THE ELCTRONIC FLIGHT BAG:

It’s an electronic management device that is currently being used to help flight crew with their management flight task more efficiently without the use of paper. It purpose is to replace the use of paper based reference manuals and materials found in the flight deck. It includes other functions such as an e-Logbook, maintenance pages for engineer and performance calculations.

THE DIFFERENT CLASSES OF THE EFB:

There are currently three classes of EFB:

1. Class 1 – Standard portable computers classified as PED such as personal computers and handheld electronic devices.
2. Class 2 – Classified as PED’s as well but mounted in the flight deck in clear view of the flight crew during all phases of flight.
3. Class 3 – Must be under design control and subjected to the regulatory certification and airworthiness requirements.

INCIDENTS INVOLVING THE INCORRECT USE OF EFB – PERFORMANCE CALCULATIONS:

CASE 1

On the 12th of December 2009, an Airbus A340 departing out of London Heathrow departed with VR and V2 values significantly lower than required for the actual takeoff. The aircraft managed to get airborne albeit with the rotation slower than normal and with degraded climb performance.
The error occurred due to a late change in to the zero fuel weight which led to the procedures being conducted out of sequence. The crew used the expected landing weight instead of the actual takeoff weight as the input selected into the electronic flight bag. This led to the erroneous speed of VR 143 and V2 151 instead of the correct speeds of 157 and 167. As another result, the power setting obtained from the EFB and used was much reduced, FLEX 74° instead of 63°.

CASE 2

a6erg3.jpg Emirates%20tailstrike%201.JPG
Emirates Tail Strike Embedded from[http://aaegmod.files.wordpress.com/2009/03/a6erg3.jpg] on 21 September 2010 Emirates Tail Strike, Embedded from[http://www.flightglobal.com/blogs/unusual-attitude/Emirates%20tailstrike%201.JPG on 21 September 2010

On March 2009, an Airbus A340 departing from Runway 16 at Melbourne Airport bound for Dubai, United Arab Emirates, struck the runway on takeoff. During pre-flight, the erroneous takeoff weight was entered into the performance software of the laptop used by the flight crew. Cross checking between the pilots didn’t detect the incorrect data entry and erroneous speeds. As a result, the tail of the aircraft struck the runway surface on takeoff with the reduced thrust and speeds. The captain selected full takeoff power and the aircraft managed to climb. After jettisoning the fuel to reduce the aircraft weight to it's certified maximum landing weight, the pilot returned to Melbourne for a landing.

STUDY DONE BY APPLIED ANTROPOLOGY LABORATORY:

A study done by Applied Anthropology Laboratory at the behest of BEA and DGAC (French CAA) identified the following issues:

  1. Errors committed which are related to takeoff data are frequent although most of the time are “trapped” and identified and rectified by SOP and mental calculation
  2. The errors are normally committed when inserting the data into the EFB rather than the FMS.
  3. There have been frequent cases where ZFW was used instead of takeoff weight for performance calculation.
  4. A survey carried out found that half of the respondents had experience in erroneous takeoff parameters
  5. There are a large number of tasks to be performed under time pressure with late changes to takeoff weights
  6. The crosschecking of the takeoff parameters can be ineffective if the accuracy of the data itself is not verified.
  7. Reinsertion of new data into the FMS doesn’t generate an alert to the crew
  8. Software makes it difficult to memorise “ballpark” figures for speeds to corresponding weights.

Crew workload are high during the periods where erroneous data entry have occurred. Time pressure and distraction have being cited as causal factors.

HAZARDS:

The hazards associated with the EFB are:

  1. The data generated is rarely challenged by the flight crew and accepted the correct figures. As we have seen, incorrect inputs can occur, resulting in incorrect takeoff speeds.
  2. Zero Fuel Weights (ZFW) are used instead of Take Off Weights as data entries into the performance software, especially when time pressure and workload increases.
  3. Takeoff speeds calculation are based on specific configurations. Any change in any parameters environmental (changes in QNH, temperature, wind), airfield, or aircraft configuration will invalidate the takeoff speeds.
  4. Time pressure increases the likelihood of incorrect data entry.

THREATS:

The threats associated with the EFB are:

  1. Incorrect calculation of the takeoff performance may jeopardize safety margin for takeoff – obstacle clearances, RTO margins and stall margins after takeoff.
  2. Speeds generated are lower than expected leading to Tail strikes, high speed rejected takeoff and overruns.

MITIGATING ACTIONS:

The mitigating actions are:

  1. Independent entry and computation of takeoff performance which is then validated by the other crew.
  2. Question all takeoff speeds generated, especially on flights with significant fuel carriage and close V1 and VR.
  3. Minimise distraction (closing the cockpit door) and making time (slowing down) to ensure data is valid. For changes during taxiing, don’t multi task, stop and recomputed with all crewmembers crosschecking and verifying data accuracy and entry.
  4. Management of workload and time pressure. Complete tasks early. Don’t take shortcuts. Recognize the need to slow down.

References

1. United Kingdom Civil Aviation Authority. (July 2010). Retrieved 18 september 2010, from http://www.aaib.gov.uk/publications/bulletins/july_2010/airbus_a340_642__g_vyou.cfm

2. Use of erroneous parameters at takeoff. Retrieved 18 September 2010, from http://www.skybrary.aero/index.php/Use_of_Erroneous_Parameters_at_Take-Off

Want to know more?

Skybrary: http://www.skybrary.aero/index.php/Use_of_Erroneous_Parameters_at_Take-Off
Eurocontrol: http://www.eurocontrol.int/airports/gallery/content/public/pdf/EFB.pdf


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