Small transport aircraft had trouble receiving signals for GPS navigation.

Attributes
ACN	418715
Time
Date	199810
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : dut airport : 4oa airport : 40a airport : dut
State Reference	AK
Altitude	msl bound lower : 11500 msl bound upper : 11500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air taxi
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 135
Flight Phase	climbout : intermediate altitude cruise other
Route In Use	enroute : direct
Flight Plan	VFR
Person 1
Affiliation	company : air taxi
Function	flight crew : single pilot
Qualification	other other : other pilot : atp pilot : cfi
Experience	flight time last 90 days : 200 flight time total : 6300 flight time type : 250
ASRS Report	418715
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	other flight crewa
Resolutory Action	other other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Loss of GPS signal. I departed 40A at XA56 and did not receive sufficient GPS signal to navigation. The king kln 89B GPS indicated it was receiving only 2 satellites, SV27 and SV31. 20 mins later, the GPS began to work, indicating that it was receiving 5 satellites, SV02, 13, 26, 27, 31. 5 mins later, it indicated raim was not available. 30 mins later (40 mi out of dut), it indicated receiving 8 satellites, with raim available. There was no indication of any fault with the GPS receiver. No hazard resulted because NDB navigation was available. I am reporting this occurrence because it demonstrates a lack of reliability I have observed with the GPS system.

Original NASA ASRS Text

Title: SMT ACFT HAD TROUBLE RECEIVING SIGNALS FOR GPS NAV.

Narrative: LOSS OF GPS SIGNAL. I DEPARTED 40A AT XA56 AND DID NOT RECEIVE SUFFICIENT GPS SIGNAL TO NAV. THE KING KLN 89B GPS INDICATED IT WAS RECEIVING ONLY 2 SATELLITES, SV27 AND SV31. 20 MINS LATER, THE GPS BEGAN TO WORK, INDICATING THAT IT WAS RECEIVING 5 SATELLITES, SV02, 13, 26, 27, 31. 5 MINS LATER, IT INDICATED RAIM WAS NOT AVAILABLE. 30 MINS LATER (40 MI OUT OF DUT), IT INDICATED RECEIVING 8 SATELLITES, WITH RAIM AVAILABLE. THERE WAS NO INDICATION OF ANY FAULT WITH THE GPS RECEIVER. NO HAZARD RESULTED BECAUSE NDB NAV WAS AVAILABLE. I AM RPTING THIS OCCURRENCE BECAUSE IT DEMONSTRATES A LACK OF RELIABILITY I HAVE OBSERVED WITH THE GPS SYS.

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