Narrative:

After pushing at four minutes early; and taxiing out on both engines; we had to deice. It was actively snowing at push time and during takeoff roll. After being disconnected from our tug; we were blocked from our taxi route for approximately 10 minutes as another carrier blocked our progress. Once in the south deice pad; we were the second company aircraft to be deiced with the two-step type I and type iv deice procedures. We had planned a flap 5 max power takeoff; and the speeds where 137. 137; 140 something. After leaving the deice pad; and taxiing to the 1L; we held short of the 1L ILS critical area; then were cleared for takeoff on 1L. The runway was being reported 'wet good' but I mentally noted there was a great deal of snow/ice on the runway; particularly the left side of the runway. We performed all checklists and operated slowly and methodically to not rush. We were not in a hurry; but rather extremely vigilante and operated at a much slower pace than I normally operated. After waiting for both engines to spool up to 40 percent N1 and had achieved symmetric thrust; I advanced both start levers and selected toga. The aircraft accelerated rapidly; and approximately 80 knots; the aircraft nose turned to the left approximately 15 to 20 degrees and we were then accelerating toward the edge of the runway. I applied right rudder and right aileron but the aircraft did not correct. At approximately; 100 knots I knew we needed to reject or get the aircraft tracking back to the right. Rejecting was not a great option given runway contamination. I immediately grabbed the nose wheel tiller with my left hand turning it to the right and took my right hand from the throttles to apply right aileron. The aircraft responded and we tracked back toward centerline and rotated uneventfully. First; I think the 'wet good'; 'wet fair'; 'wet poor' and mu values are ridiculous to try to correlate. I don't even know if there is any standardization from the people who take mu readings; but I do know what I saw and took off on yesterday wasn't the same 'wet good' I see after a light summer rainfall. I think our training department needs to educate our pilots on exactly how mu values are calculated. I have quite a few questions regarding the mu values and the process to obtain these values. I question the logic of mu values given; I have no clue how their values are calculated; nor if they are the best parts of the runway. I want the mu values on the worse part of the runway; since I could find myself on the worse mu portion of the runway during takeoff and landing. A) when an mu value is given; is there any requirement for the mu truck driver to drive down the most contaminated portions of a runway (e.g. The left or right sides) or do they stay in the center of the runway and do their braking on the cleanest portion of the runway? B) do the trucks actually test the portions of the runways around 20-25\' from the runway edge or do they stay on the centerline? C) how often is a mu value required to be updated; when it is actively snowing or other frozen precipitin is falling? D) has any company safety ever been in a truck when the mu truck does the brake action reporting in a place like mdw; buf; in the middle of a snowstorm? We get RVR at up to four portions of a runway. I get RVR is an automated system versus a human driving down a runway and hitting his brakes in a truck. Every time I see a guy doing one; the truck is in the center of the runway; where the nose tire would be rolling; not the left and right main tires. This makes zero sense to me. Along with 'wet good' on a snow and ice covered runway in mke being equal to a 'wet good' on a rainy july afternoon after a rain shower passes the field. 2) in xx years of flying both military transport aircraft and 737 s; I have never received any training on this type of event. I think this is a great training scenario. This event was not comfortable for me in any manner. Inexperience in the left seat of the 737 wasn't a factor. I have plenty of left seat experience in other aircraft on snow covered runways. I honestly believe the left side of mke 1L was much worse than reported. Coupled with gusty winds and possible left wheel contamination that may have led to the left mains losing traction; all these factors made this a challenging takeoff.

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Original NASA ASRS Text

Title: A B737 crew questioned MU value methodology and validity after departing MKE Runway 1L with a 'Wet Good' report; when poor controllability during takeoff indicated 'Fair to Poor' conditions.

Narrative: After pushing at four minutes early; and taxiing out on both engines; we had to deice. It was actively snowing at push time and during takeoff roll. After being disconnected from our tug; we were blocked from our taxi route for approximately 10 minutes as another carrier blocked our progress. Once in the south deice pad; we were the second Company aircraft to be deiced with the two-step Type I and Type IV deice procedures. We had planned a Flap 5 Max power takeoff; and the speeds where 137. 137; 140 something. After leaving the deice pad; and taxiing to the 1L; we held short of the 1L ILS critical area; then were cleared for takeoff on 1L. The runway was being reported 'Wet Good' but I mentally noted there was a great deal of snow/ice on the runway; particularly the left side of the runway. We performed all checklists and operated slowly and methodically to not rush. We were NOT in a hurry; but rather extremely vigilante and operated at a much slower pace than I normally operated. After waiting for both engines to spool up to 40 percent N1 and had achieved symmetric thrust; I advanced both start levers and selected TOGA. The aircraft accelerated rapidly; and approximately 80 knots; the aircraft nose turned to the left approximately 15 to 20 degrees and we were then accelerating toward the edge of the runway. I applied right rudder and right aileron but the aircraft did not correct. At approximately; 100 knots I knew we needed to reject or get the aircraft tracking back to the right. Rejecting was not a great option given runway contamination. I immediately grabbed the nose wheel tiller with my left hand turning it to the right and took my right hand from the throttles to apply right aileron. The aircraft responded and we tracked back toward centerline and rotated uneventfully. First; I think the 'Wet Good'; 'Wet Fair'; 'Wet Poor' and MU values are ridiculous to try to correlate. I don't even know if there is any standardization from the people who take MU readings; but I do know what I saw and took off on yesterday wasn't the same 'Wet Good' I see after a light summer rainfall. I think our Training Department needs to educate our Pilots on exactly how MU values are calculated. I have quite a few questions regarding the MU values and the process to obtain these values. I question the logic of MU values given; I have no clue how their values are calculated; nor if they are the best parts of the runway. I want the MU values on the worse part of the runway; since I could find myself on the worse MU portion of the runway during takeoff and landing. a) When an MU value is given; is there any requirement for the MU Truck Driver to drive down the most contaminated portions of a runway (e.g. the left or right sides) or do they stay in the center of the runway and do their braking on the cleanest portion of the runway? b) Do the trucks actually test the portions of the runways around 20-25\' from the runway edge or do they stay on the centerline? c) How often is a MU value required to be updated; when it is actively snowing or other frozen precipitin is falling? d) Has any Company Safety ever been in a truck when the MU truck does the brake action reporting in a place like MDW; BUF; in the middle of a snowstorm? We get RVR at up to four portions of a runway. I get RVR is an automated system versus a human driving down a runway and hitting his brakes in a truck. Every time I see a guy doing one; the truck is in the center of the runway; where the nose tire would be rolling; not the left and right main tires. This makes zero sense to me. Along with 'Wet Good' on a snow and ice covered runway in MKE being equal to a 'Wet Good' on a rainy July afternoon after a rain shower passes the field. 2) In XX years of flying both military transport aircraft and 737 s; I have never received any training on this type of event. I think this is a great training scenario. This event was not comfortable for me in any manner. Inexperience in the left seat of the 737 wasn't a factor. I have plenty of left seat experience in other aircraft on snow covered runways. I honestly believe the left side of MKE 1L was much worse than reported. Coupled with gusty winds and possible left wheel contamination that may have led to the left mains losing traction; all these factors made this a challenging takeoff.

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.