A helicopter cleared for an ILS approach suffers repeated failures to capture the localizer and GS f...

Attributes
ACN	845481
Time
Date	200907
Local Time Of Day	1201-1800
Place
Locale Reference	MMU.Airport
State Reference	NJ
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Make Model Name	Helicopter
Operating Under FAR Part	Part 91
Flight Phase	Initial Approach
Flight Plan	IFR
Component
Aircraft Component	Approach Coupler
Person 1
Function	Pilot Not Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 85 Flight Crew Total 9425 Flight Crew Type 100
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy Inflight Event / Encounter Weather / Turbulence

Narrative:

We were cleared to 2000 feet established inbound to moree beacon on the 227 course on the ILS 23 at mmu. After the aircraft was established inbound to moree we armed the approach for the ILS. The ILS was on the appropriate frequency 110.30. The localizer captured and switched over from the FMS and showed green needles with an invalid G/south signal. Within 1-2 seconds we lost the localizer signal and the ap disconnected and slowly pitched up with no decouple voice warning. We reengaged the localizer and it repeated the sequence of capture then loss of signal G/south first then localizer. On the third engagement at at 2nm from moree it captured both the localizer and G/south. At this point we were approximately 2600 feet descending on the G/south and established on the localizer. At approximately 1nm from moree tower called and said approach called and asked why we climbed. I reported that we had lost the localizer and G/south signals and were reestablished and correcting. Tower also reported at this time that they had a thunderstorm over the field with approximately 3/4 mile visibility in heavy rain. We witnessed a lighting strike @ 5nm away to the east. With the loss of signal and de-coupling of the ILS we should have hand flown the aircraft and maintained our altitude instead of trouble shooting the ap ILS couple issue with loss of signal. An alternative would have been to execute an immediate missed approach an inform ATC of the problem.

Original NASA ASRS Text

Title: A helicopter cleared for an ILS approach suffers repeated failures to capture the LOC and GS followed by the autopilot disconnecting. An unintended climb of 600 feet occurs.

Narrative: We were cleared to 2000 feet established inbound to MOREE beacon on the 227 course on the ILS 23 at MMU. After the aircraft was established inbound to MOREE we armed the approach for the ILS. The ILS was on the appropriate frequency 110.30. The LOC captured and switched over from the FMS and showed green needles with an invalid G/S signal. Within 1-2 seconds we lost the LOC signal and the AP disconnected and slowly pitched up with no decouple voice warning. We reengaged the LOC and it repeated the sequence of capture then loss of signal G/S first then LOC. On the third engagement at at 2nm from MOREE it captured both the LOC and G/S. At this point we were approximately 2600 feet descending on the G/S and Established on the LOC. At approximately 1nm from MOREE tower called and said approach called and asked why we climbed. I reported that we had lost the LOC and G/S signals and were reestablished and correcting. Tower also reported at this time that they had a thunderstorm over the field with approximately 3/4 mile visibility in heavy rain. We witnessed a lighting strike @ 5nm away to the east. With the loss of signal and de-coupling of the ILS we should have hand flown the aircraft and maintained our altitude instead of trouble shooting the AP ILS couple issue with loss of signal. An alternative would have been to execute an immediate missed approach an inform ATC of the problem.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

A helicopter cleared for an ILS approach suffers repeated failures to capture the localizer and GS followed by the autopilot disconnecting. An unintended climb of 600 feet occurs.