Aircraft overshot assigned altitude and came in close proximity to an IFR aircraft above him.

Attributes
ACN	107914
Time
Date	198904
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : bos
State Reference	MA
Altitude	msl bound lower : 4700 msl bound upper : 5000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : bos artcc : zkc
Operator	common carrier : air carrier
Make Model Name	Small Transport, Low Wing, 2 Turboprop Eng
Flight Phase	climbout : intermediate altitude
Route In Use	departure other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air taxi
Make Model Name	Light Transport, High Wing, 2 Turboprop Eng
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : departure
Qualification	controller : radar
ASRS Report	107914
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : overshoot conflict : airborne less severe non adherence : clearance non adherence : required legal separation
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Miss Distance	horizontal : 9000 vertical : 300
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

I was working the initial departure position at bos approach. Small transport departed runway 27 heading 250 degrees. I issued a climb to 4000' MSL and issued crossing traffic at 10 O'clock, 3 mi, northeast bound at 5000', an light transport. The pilot said he was IMC and would not see the traffic. I said, 'roger, contact bos departure on 127.2.' he acknowledged. The next thing I saw (about 1 or 2 mins later) was his altitude readout indicating 4700'. As I went to warn the lincoln sector controller I heard him issuing avoidance vectors to the light transport. They passed within 300' and 1 1/2 mi (approximately). I then observed the small transport altitude descend rapidly to 4000'. I later asked the other controller if he had issued the descent. He said he had not. This would indicate that the pilot realized his error and corrected his altitude. It should be noted that bos approach had undergone a major airspace reorganization only 3 days earlier, which included changes in frequency and altitude assignments.

Original NASA ASRS Text

Title: ACFT OVERSHOT ASSIGNED ALT AND CAME IN CLOSE PROX TO AN IFR ACFT ABOVE HIM.

Narrative: I WAS WORKING THE INITIAL DEP POS AT BOS APCH. SMT DEPARTED RWY 27 HDG 250 DEGS. I ISSUED A CLB TO 4000' MSL AND ISSUED XING TFC AT 10 O'CLOCK, 3 MI, NE BOUND AT 5000', AN LTT. THE PLT SAID HE WAS IMC AND WOULD NOT SEE THE TFC. I SAID, 'ROGER, CONTACT BOS DEP ON 127.2.' HE ACKNOWLEDGED. THE NEXT THING I SAW (ABOUT 1 OR 2 MINS LATER) WAS HIS ALT READOUT INDICATING 4700'. AS I WENT TO WARN THE LINCOLN SECTOR CTLR I HEARD HIM ISSUING AVOIDANCE VECTORS TO THE LTT. THEY PASSED WITHIN 300' AND 1 1/2 MI (APPROX). I THEN OBSERVED THE SMT ALT DSND RAPIDLY TO 4000'. I LATER ASKED THE OTHER CTLR IF HE HAD ISSUED THE DSCNT. HE SAID HE HAD NOT. THIS WOULD INDICATE THAT THE PLT REALIZED HIS ERROR AND CORRECTED HIS ALT. IT SHOULD BE NOTED THAT BOS APCH HAD UNDERGONE A MAJOR AIRSPACE REORGANIZATION ONLY 3 DAYS EARLIER, WHICH INCLUDED CHANGES IN FREQ AND ALT ASSIGNMENTS.

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.