C172 pilot had altitude deviation and erratic track in IMC while flying the VOR-B approach to F29.

Attributes
ACN	518074
Time
Date	200107
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : irw.vor
State Reference	OK
Altitude	msl single value : 3000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : okc.tracon tower : ipt.tower
Operator	general aviation : personal
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Navigation In Use	other vortac
Flight Phase	descent : approach
Route In Use	approach : instrument non precision
Flight Plan	IFR
Person 1
Affiliation	other
Function	flight crew : single pilot
Qualification	pilot : private pilot : instrument
Experience	flight time last 90 days : 17 flight time total : 251 flight time type : 251
ASRS Report	518074
Person 2
Affiliation	government : faa
Function	controller : approach
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude inflight encounter : weather non adherence : published procedure other anomaly other other spatial deviation
Independent Detector	other controllera other flight crewa
Resolutory Action	controller : issued alert controller : issued new clearance controller : provided flight assist flight crew : executed missed approach none taken : detected after the fact
Supplementary
Problem Areas	Weather Flight Crew Human Performance Aircraft
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

While flying the VOR-B to F29, had difficulty maintaining course after crossing IAF, which led to s-turns down the approach course. The VOR indicator seemed to be sluggish in its indications, and I overcorrected, aggravating the s-turns. Also, with the distraction of troubleshooting the problem, I briefly went below the altitude limit for the initial approach segment. ATC informed me of my position along the way, and then vectored me around for a second approach when it became apparent the first one could not be completed. Second approach was better and resulted in uneventful landing. Also contributing was excessive precession in the directional gyro, causing my actual course intercept angles to be larger than what was indicated. During the turns during revectoring, I kept the directional gyro set to the magnetic compass, and better anticipated the VOR indicator response. I should have picked up the VOR problem sooner, abandoned the approach, and done the troubleshooting elsewhere, rather than continuing. This was also my first solo actual IMC approach since being recently instrument rated. I intend to get as much actual IMC experience as possible, in order to fly well and safely in IMC.

Original NASA ASRS Text

Title: C172 PLT HAD ALTDEV AND ERRATIC TRACK IN IMC WHILE FLYING THE VOR-B APCH TO F29.

Narrative: WHILE FLYING THE VOR-B TO F29, HAD DIFFICULTY MAINTAINING COURSE AFTER XING IAF, WHICH LED TO S-TURNS DOWN THE APCH COURSE. THE VOR INDICATOR SEEMED TO BE SLUGGISH IN ITS INDICATIONS, AND I OVERCORRECTED, AGGRAVATING THE S-TURNS. ALSO, WITH THE DISTR OF TROUBLESHOOTING THE PROB, I BRIEFLY WENT BELOW THE ALT LIMIT FOR THE INITIAL APCH SEGMENT. ATC INFORMED ME OF MY POS ALONG THE WAY, AND THEN VECTORED ME AROUND FOR A SECOND APCH WHEN IT BECAME APPARENT THE FIRST ONE COULD NOT BE COMPLETED. SECOND APCH WAS BETTER AND RESULTED IN UNEVENTFUL LNDG. ALSO CONTRIBUTING WAS EXCESSIVE PRECESSION IN THE DIRECTIONAL GYRO, CAUSING MY ACTUAL COURSE INTERCEPT ANGLES TO BE LARGER THAN WHAT WAS INDICATED. DURING THE TURNS DURING REVECTORING, I KEPT THE DIRECTIONAL GYRO SET TO THE MAGNETIC COMPASS, AND BETTER ANTICIPATED THE VOR INDICATOR RESPONSE. I SHOULD HAVE PICKED UP THE VOR PROB SOONER, ABANDONED THE APCH, AND DONE THE TROUBLESHOOTING ELSEWHERE, RATHER THAN CONTINUING. THIS WAS ALSO MY FIRST SOLO ACTUAL IMC APCH SINCE BEING RECENTLY INST RATED. I INTEND TO GET AS MUCH ACTUAL IMC EXPERIENCE AS POSSIBLE, IN ORDER TO FLY WELL AND SAFELY IN IMC.

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.