<< >> NASA ASRS Report 1432176, March 2017

B737 captain reported a dual eec default to alternate mode during taxi out. Following the addition of an MEL; the captain's airspeed indication was low on takeoff but not discovered in time to reject. The first officer's airspeed indication was normal and the flight returned to the departure airport.

Attributes
ACN	1432176
Time
Date	201703
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Daylight
Aircraft 1
Make Model Name	B737-700
Operating Under FAR Part	Part 121
Flight Phase	Taxi Takeoff
Flight Plan	IFR
Component
Aircraft Component	Pitot-Static System
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 173
Events
Anomaly	Aircraft Equipment Problem Critical Flight Deck / Cabin / Aircraft Event Other / Unknown

Narrative:

We were delayed one hour and fourteen minutes for weather. Taxiing to runway both eec went to alternate mode on overhead panel. We contacted company operations center and added an MEL for both eec in alternate mode. On takeoff roll above 80 knots we got an amber IAS disagree. Then the captain airspeed was displaying 45 knots. As I was about to abort the takeoff; the first officer called V1. I stated I had no airspeed as we continued the takeoff. At about 700 ft I transferred control to first officer. As we climbed through 2000 ft captain's airspeed started to read. At 5000' 210 knots on standby and first officer a/south captain a/south reading 280 knots. At this time we told ATC we needed to return. We turned on to downwind; accomplished QRH checklist; called company; call flight attendants and informed passengers we are returning. On approach to land at 140 knots; my airspeed was reading 210 knots then dropped to 100 knots then 90 knots. At this time we got flap relief from 30 to 25 to 30. We also got verbal lower airspeed warnings. Landing was normal. Our MEL required a max power takeoff. We had 23 passengers with a V1 of 113 knots. From 80 knots to 113 knots gave us very little time to decide to abort or fly.

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Original NASA ASRS Text

Title: B737 Captain reported a dual EEC default to alternate mode during taxi out. Following the addition of an MEL; the Captain's airspeed indication was low on takeoff but not discovered in time to reject. The First Officer's airspeed indication was normal and the flight returned to the departure airport.

Narrative: We were delayed one hour and fourteen minutes for weather. Taxiing to runway both EEC went to alternate mode on overhead panel. We contacted Company Operations Center and added an MEL for both EEC in alternate mode. On takeoff roll above 80 knots we got an amber IAS Disagree. Then the Captain airspeed was displaying 45 knots. As I was about to abort the takeoff; the First Officer called V1. I stated I had no airspeed as we continued the takeoff. At about 700 FT I transferred control to First Officer. As we climbed through 2000 FT Captain's airspeed started to read. At 5000' 210 knots on standby and First Officer A/S Captain A/S reading 280 knots. At this time we told ATC we needed to return. We turned on to downwind; accomplished QRH Checklist; called Company; call flight attendants and informed passengers we are returning. On approach to land at 140 knots; My Airspeed was reading 210 knots then dropped to 100 knots then 90 knots. At this time we got flap relief from 30 to 25 to 30. We also got verbal Lower Airspeed Warnings. Landing was normal. Our MEL required a max power takeoff. We had 23 passengers with a V1 of 113 knots. From 80 knots to 113 knots gave us very little time to decide to abort or fly.

Data retrieved from NASA's ASRS site 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.