COUNTER DRUM POINTER ALTIMETER EXEMPTION POLICY

1. COUNTER DRUM POINTER ALTIMETER EXEMPTION POLICY

2. OBJECTIVE • Discuss requirement for CDP altimeters in relation to Commercial Air Transport under Instrument Flight Rules or at night under Visual Flight Rules for non-pressurised aircraft operating below 10,000 ft barometric altitude

3. Current Requirements ICAO Annex 6 JAR-OPS 1.652 ICAO Annex 6 Part 1 6.9.1(c) 2 x sensitive press alts with CDP or equivalent – 3 pointer or drum pointer not acceptable JAR-OPS 1.652(c) and (k)(2) 2 x sensitive pressure alts calibrated in hectopascals/ millibars adjustable for flight conditionsand must have CDP presentation Difference Exemption EU-OPS ?

4. EQUIVALENT SAFETY CASE ICAO ANNEX 6 Part II 6.6 (c) – International GA Aeroplanes IFR A sensitive pressure altimeter is required (Drum-Pointer Altimeters not recommended) No requirement for Counter Drum Pointer Altimeters ICAO ANNEX 6 Part III 4.10(c) International Operations Helicopters IFR Two sensitive pressure altimeters with CDP or equivalent presentation (Neither three pointer or drum pointer altimeters satisfy requirement) Amendment 12 to be introduced in November 2007 removes both CDP requirement and that Three Pointer or Drum Pointer Altimeters do not satisfy requirement JAR-OPS 3.652(c) and (m)(1) CAT – Helicopters IFR or night VFR Two sensitive pressure altimeters calibrated in feet, with sub-scale settings calibrated In hectopascals/millibars, adjustable for any barometric pressure likely to be set During Flight. For single pilot Ops one pressure altimeter may be substituted by a Radio Altimeter No requirement for Counter Drum Pointer Altimeters

5. Mandatory Occurrence Reports A search of the UK CAA MOR database revealed 8 incidents since 1976 where a contributory factor has been determined as misreading of an altimeter whilst airborne. Of these: 4 relate to large commercial transport aircraft with Counter Drum Pointer Altimeters fitted 1 is a private category Piper PA 28 aircraft with the error assigned to poor piloting skills (not subject of this presentation) 1 is a private Yak 42 aircraft with the primary altimeter display in meters - with this being assigned as the primary causal factor (not subject of this presentation) 1 is a Hughes 269 helicopter (not subject of this presentation) 1 is a commercial Piper PA 31 aircraft with altimetry error assigned to non-setting of 1013.2 Mb at the transition level INCIDENT DATA

6. UK SITUATION • Currently: • 13 JAR-OPS 1 Operators • 15 different aircraft types • 53 aircraft • Aircraft range from Piper PA-27 to De Havilland DC6 and are currently exempted IAW JAA Admin and Guidance Material TGL 33 until 31st March 2007

7. THREE POINTER ALTIMETER

8. COUNTER DRUM POINTER ALTIMETER

9. COUNTER POINTER ALTIMETER

10. REFIT COSTS ANALYSIS Refit costs estimates for re-equipping currently exempted aircraft Swiss Counter Drum Pointer Altimeter X 2 @ € 7852 € 15704 Minor Modification Approval UK CAA € Nil EASA STC Approval € 600 Part-21 Organisation design cost € 1037 Part-145 Organisation labour cost – 15 Man-Hours € 1000 Total Per Airframe not counting downtime costs € 18341 Total for currently exempted aircraft € 972073 * Note some savings may be made due to Modification and STC approvals only required once per aircraft type

11. DISCUSSION Counter Pointer Altimeter The Counter Pointer Altimeter has been established as the main cause of Flight Crew altimeter interpretation errors. The most significant case is during the approach phase of flight and has led to several aircraft landing accidents.Use of this type of altimeter should be discouraged Counter Drum Pointer Altimeter Research has shown that the Counter Drum Pointer Altimeter is the most easily read instrument with the least instances of misinterpretation above 10,000ft and on final approach

12. Discussion (Cont) Three Pointer Altimeter The Three Pointer Altimeter has readability issues when used in operational circumstances above 10,000ft however, when used below this height, the ten thousands ft pointer remains at the 12 o clock position and does not interfere with the readability of the instrument. Many Three Pointer Altimeters have the ten thousands pointer as a small white triangle on the circumference of the dial Readability below 10.000ft is unambiguous and significantly, at the approach and landing phase of flight, interpretation errors are negligible

13. PROPOSAL Unpressurised aircraft authorised for operations below 10,000ft barometric altitude should be allowed to utilise either Counter Drum Pointer Altimeters or Three Pointer Altimeters or, a combination of both with the Counter Drum Pointer Altimeter in the Captains position JAR-OPS 1.652(c) Two sensitive pressure altimeters calibrated in feet with sub-scale settings, calibrated in hectopascals/millibars, adjustable for any barometric pressure likely to be set during flight. For aircraft operations above 10.000ft barometric altitude, both altimeters must have Counter Drum Pointer or equivalent presentations Note: Counter Pointer Altimeters are not permitted and when a combination of altimeter types is used the Counter Drum Pointer Altimeter must be in the Captains position