Captain of an medium large transport landed short of the displaced threshold.

Attributes
ACN	319960
Time
Date	199510
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : mdw
State Reference	IL
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	DC-9 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	landing other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	other other : other pilot : atp pilot : cfi
Experience	flight time last 90 days : 50 flight time total : 18100 flight time type : 4426
ASRS Report	319960
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	inflight encounter other non adherence other other anomaly other other anomaly other
Independent Detector	other flight crewa
Resolutory Action	none taken : unable other
Consequence	Other
Supplementary
Primary Problem	Weather
Air Traffic Incident	Pilot Deviation other

Narrative:

Air carrier aircraft that I was flying touched down just prior to displaced threshold on runway 31C at chicago (mdw) on date/time indicated above. Surface wind being reported as 100/08 or slight quartering tailwind. All the way down the ILS we experienced a significant tailwind requiring N1 settings 6-8 percent below normal. I flew a coupled ILS to approximately 150-200 ft AGL at which time I turned off autoplt and assumed the VASI for visual reference. At 100 ft I was precisely on GS according to the VASI. At approximately 30 ft to 50 ft AGL I reduced the power to idle as with all normal approachs for this model DC9. However, the tailwind apparently dispatched in the roundout/flare causing a sink rate resulting in early touchdown, perhaps as much as 1/2 to 1 aircraft lengths prior to stripe. Contributing factors: infamous short runway with obstructions. Tailwind all the way down final increasing one's desire to have aircraft touch down timely rather than float. VASI lights fly you exactly to the displaced threshold stripe. Loss of tailwind as aircraft descends below building ht (75 ft).

Original NASA ASRS Text

Title: CAPT OF AN MLG LANDED SHORT OF THE DISPLACED THRESHOLD.

Narrative: ACR ACFT THAT I WAS FLYING TOUCHED DOWN JUST PRIOR TO DISPLACED THRESHOLD ON RWY 31C AT CHICAGO (MDW) ON DATE/TIME INDICATED ABOVE. SURFACE WIND BEING RPTED AS 100/08 OR SLIGHT QUARTERING TAILWIND. ALL THE WAY DOWN THE ILS WE EXPERIENCED A SIGNIFICANT TAILWIND REQUIRING N1 SETTINGS 6-8 PERCENT BELOW NORMAL. I FLEW A COUPLED ILS TO APPROX 150-200 FT AGL AT WHICH TIME I TURNED OFF AUTOPLT AND ASSUMED THE VASI FOR VISUAL REF. AT 100 FT I WAS PRECISELY ON GS ACCORDING TO THE VASI. AT APPROX 30 FT TO 50 FT AGL I REDUCED THE PWR TO IDLE AS WITH ALL NORMAL APCHS FOR THIS MODEL DC9. HOWEVER, THE TAILWIND APPARENTLY DISPATCHED IN THE ROUNDOUT/FLARE CAUSING A SINK RATE RESULTING IN EARLY TOUCHDOWN, PERHAPS AS MUCH AS 1/2 TO 1 ACFT LENGTHS PRIOR TO STRIPE. CONTRIBUTING FACTORS: INFAMOUS SHORT RWY WITH OBSTRUCTIONS. TAILWIND ALL THE WAY DOWN FINAL INCREASING ONE'S DESIRE TO HAVE ACFT TOUCH DOWN TIMELY RATHER THAN FLOAT. VASI LIGHTS FLY YOU EXACTLY TO THE DISPLACED THRESHOLD STRIPE. LOSS OF TAILWIND AS ACFT DSNDS BELOW BUILDING HT (75 FT).

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.