UH60 flight crew experienced two altitude excursions after disconnecting the stabilator from the aut...

Narrative:

While flying IFR in VMC my aircraft we experienced an airspeed fault capsule advisory light and flight path stabilization (fps) caution light. I attempted to reset the airspeed fault capsule advisory light but was unable to do so for more than a few seconds. My airspeed indicator was reading approximately 90 KIAS while my copilot's was reading 110 KIAS. At this point I had the crew members in the back read the emergency procedure. I followed the procedure to control the axis manually and took our stabilator out of the auto mode; which is required by our operators manual because continued flight above 70 KIAS with the stabilator in the auto mode is unsafe; and slewed it to 0 degrees per our emergency procedure. When I took this action the other pilot was not ready for the aircraft to climb when I slewed the stabilator from 8 degrees down to 0 degrees. This action made the aircraft climb out of our assigned altitude of 11;000 feet but not more than 200 feet above. I made the call to center that I needed to turn around and return to [departure airport] and that I was not declaring an emergency. I was unable to reach center and was relaying through my sister ship that was located on the same airway but was at 12;000 feet and 5 or more miles behind me. When we got word from our sister aircraft we started our turn and the aircraft climbed again to approximately 11;400 feet. I believe this to be because the handling characteristics of the aircraft changed due to me slewing the stabilator to 0. After making the turn my airspeed indicator was erratic and was displaying between 0 and 140 KIAS while my copilot's remained steady at 100 to 110 KIAS. I could see our sister aircraft on the airway high and to our right side and that is why center called a pilot deviation and asked me to contact them when I landed. In hindsight I should have declared an emergency.

Original NASA ASRS Text

Title: UH60 flight crew experienced two altitude excursions after disconnecting the stabilator from the auto mode due to a Flight Path Stabilization caution light. ATC advised of a Pilot Deviation due to the proximity of an accompanying helicopter in trail and 1;000 feet above the reporter's aircraft.

Narrative: While flying IFR in VMC my aircraft we experienced an Airspeed Fault Capsule advisory light and Flight Path Stabilization (FPS) caution light. I attempted to reset the Airspeed Fault Capsule advisory light but was unable to do so for more than a few seconds. My airspeed indicator was reading approximately 90 KIAS while my copilot's was reading 110 KIAS. At this point I had the crew members in the back read the emergency procedure. I followed the procedure to control the axis manually and took our stabilator out of the auto mode; which is required by our operators manual because continued flight above 70 KIAS with the stabilator in the auto mode is unsafe; and slewed it to 0 degrees per our emergency procedure. When I took this action the other pilot was not ready for the aircraft to climb when I slewed the stabilator from 8 degrees down to 0 degrees. This action made the aircraft climb out of our assigned altitude of 11;000 feet but not more than 200 feet above. I made the call to Center that I needed to turn around and return to [departure airport] and that I was not declaring an emergency. I was unable to reach Center and was relaying through my sister ship that was located on the same airway but was at 12;000 feet and 5 or more miles behind me. When we got word from our sister aircraft we started our turn and the aircraft climbed again to approximately 11;400 feet. I believe this to be because the handling characteristics of the aircraft changed due to me slewing the stabilator to 0. After making the turn my airspeed indicator was erratic and was displaying between 0 and 140 KIAS while my copilot's remained steady at 100 to 110 KIAS. I could see our sister aircraft on the airway high and to our right side and that is why Center called a pilot deviation and asked me to contact them when I landed. In hindsight I should have declared an emergency.

Data retrieved from NASA's ASRS site as of July 2013 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.

Attributes
ACN	1049877
Time
Date	201211
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Make Model Name	S-70/UH-60 Blackhawk/Seahawk/Pavehawk/Knighthawk
Flight Phase	Cruise
Route In Use	Airway V204
Flight Plan	IFR
Component
Aircraft Component	Airspeed Indicator
Person 1
Function	Captain
Qualification	Flight Crew Commercial Flight Crew Instrument
Experience	Flight Crew Last 90 Days 60 Flight Crew Total 1980 Flight Crew Type 1500
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Excursion From Assigned Altitude
Miss Distance	Horizontal 5280 Vertical 600

UH60 flight crew experienced two altitude excursions after disconnecting the stabilator from the auto mode due to a flight path stabilization caution light. ATC advised of a pilot deviation due to the proximity of an accompanying helicopter in trail and 1;000 feet above the reporter's aircraft.