<< >> NASA ASRS Report 123306, September 1989

Small aircraft pilot experiences pitot static problems on approach after flying through hail. Instrument indications erratic.

Attributes
ACN	123306
Time
Date	198909
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : sts
State Reference	CA
Altitude	msl bound lower : 1900 msl bound upper : 3000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : sts
Operator	general aviation : instructional
Make Model Name	Small Aircraft, High Wing, 1 Eng, Fixed Gear
Flight Phase	cruise other descent : approach descent other
Route In Use	arrival other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : private pilot : commercial pilot : instrument
Experience	flight time last 90 days : 10 flight time total : 278 flight time type : 24
ASRS Report	123306
Person 2
Affiliation	government : faa
Function	controller : local
Qualification	controller : non radar
Events
Anomaly	aircraft equipment problem : critical altitude deviation : crossing restriction not met altitude deviation : overshoot inflight encounter : weather non adherence : published procedure other spatial deviation
Independent Detector	other flight crewa
Resolutory Action	flight crew : became reoriented flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	other

Narrative:

A descent was initiated inside fix for descent. Pilot noticed unusual altitude and vsi indications which indicated aircraft may be lower and in steeper descent rate than was previously indicated. (Altimeter and vsi were simultaneously jumping nearly instantaneously to several hundred feet lower and sharply increased descent rate.) note: no apparent turbulence at all. This occurred repeatedly over a short time period during this segment. Descent altitude was stopped immediately as this indicated a possible pitot static/static system malfunction and aircraft could be lower than indicated.

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Original NASA ASRS Text

Title: SMA PLT EXPERIENCES PITOT STATIC PROBLEMS ON APCH AFTER FLYING THROUGH HAIL. INSTRUMENT INDICATIONS ERRATIC.

Narrative: A DSCNT WAS INITIATED INSIDE FIX FOR DSCNT. PLT NOTICED UNUSUAL ALT AND VSI INDICATIONS WHICH INDICATED ACFT MAY BE LOWER AND IN STEEPER DSCNT RATE THAN WAS PREVIOUSLY INDICATED. (ALTIMETER AND VSI WERE SIMULTANEOUSLY JUMPING NEARLY INSTANTANEOUSLY TO SEVERAL HUNDRED FEET LOWER AND SHARPLY INCREASED DSCNT RATE.) NOTE: NO APPARENT TURBULENCE AT ALL. THIS OCCURRED REPEATEDLY OVER A SHORT TIME PERIOD DURING THIS SEGMENT. DSCNT ALT WAS STOPPED IMMEDIATELY AS THIS INDICATED A POSSIBLE PITOT STATIC/STATIC SYSTEM MALFUNCTION AND ACFT COULD BE LOWER THAN INDICATED.

Data retrieved from NASA's ASRS site as of August 2007 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.