Narrative:

Contrary to flight operations technician's comments, I could find nothing in the fom that tells a pilot that despite the reported visibility, the actual visibility from the cockpit could be zero. During the final stage of landing at mia, there was a heavy downpour at the far end of runway 9L, while the first 2/3 of the runway was in the clear. The tower stated rollout runway visibility to be 2000 ft RVR -- within the limits of the approach. There were no other factors that would have precluded a safe landing, so I elected to continue the landing in the belief that we could land and slow prior to the area of reduced visibility -- should it occur. In any case, the RVR visibility was within normal limits. I assumed that we would have sufficient visibility. The first officer was flying the aircraft and doing fine. We did encounter the rain. The downpour, however, was torrential and while the RVR may have been 2000 ft, due to the huge amount of rain on the windshield, my ability to see outside of the cockpit was obscured completely except for very short glimpses near where the wiper (at the highest speed) had just swept. I took control of the aircraft during the rollout, which was uneventful. My concern is that in heavy downpours, the stated RVR does not tell the story of actual visibility from the cockpit and in this case, I was seriously concerned that I couldn't see the runway, despite what one would be led to believe was adequate visibility. I'd like to thank those responsible for the HUD -- which likely saved our bacon. Pilots flying a non-HUD airplane would have been groping blind to find the runway. I believe that we should investigate, periodically, applying a compound similar to the product 'rain-X' to our forward windshields. This product causes the water to sheet and is much more effective than wipers -- no matter how fast they are beating. I do not know how difficult or expensive it would be to do so for the entire fleet. I do know that we would have been in jeopardy of departing the runway in a non-HUD airplane, and I know that would have been expensive. I know there are those that think we have done away with 'rain repellent' and the expense associated with it. I think the discussion needs to be reopened. 'Rain X' is a very low viscosity liquid applied monthly. How it would fare in the torturous environment of high speeds and temperature extremes, I do not know. RVR is not adequate to describe visibility during a heavy downpour. Another measure needs to be developed to adequately describe the ability of the pilot to see through the windshield while moving forward at 130 KTS. Visibility reported by transmissometers or other stationary observers is not adequate. Company reply: the transmissometers may not be positioned to give the pilot an accurate evaluation of visibility on the runway in these types of dynamic conditions. They're great for predicting what you'll get in a more homogeneous phenomenon, like fog or haze. Fast moving squalls may not fall into their field of view. Care and judgement need to be exercised in the vicinity of squalls for a variety of reasons including downdrafts and windshears. The fom has some guidance on this as well. As for the windshields, they come from ppg with a hydraulic coating on them that will eventually wear off. I am not sure right now whether we spend the money to reapply the coating. I'll find out as soon as possible and let you know. As for the HUD, it continues to pay for itself tenfold on occasions such as these. As part of the certification, numerous lndgs in the aircraft were performed with cardboard covering the entire captain's forward windscreen, essentially 0/0, with perfect touchdowns and rollouts, similar to our landing. We are a lucky fleet to have this pwrful device.

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Original NASA ASRS Text

Title: B737-700 CAPT REGRETS THE REMOVAL OF THE RAIN REPELLENT SYS AND THINKS IT SHOULD BE REPLACED WITH A COMMERCIAL AUTOMOTIVE RAIN REPELLENT.

Narrative: CONTRARY TO FLT OPS TECHNICIAN'S COMMENTS, I COULD FIND NOTHING IN THE FOM THAT TELLS A PLT THAT DESPITE THE RPTED VISIBILITY, THE ACTUAL VISIBILITY FROM THE COCKPIT COULD BE ZERO. DURING THE FINAL STAGE OF LNDG AT MIA, THERE WAS A HVY DOWNPOUR AT THE FAR END OF RWY 9L, WHILE THE FIRST 2/3 OF THE RWY WAS IN THE CLR. THE TWR STATED ROLLOUT RWY VISIBILITY TO BE 2000 FT RVR -- WITHIN THE LIMITS OF THE APCH. THERE WERE NO OTHER FACTORS THAT WOULD HAVE PRECLUDED A SAFE LNDG, SO I ELECTED TO CONTINUE THE LNDG IN THE BELIEF THAT WE COULD LAND AND SLOW PRIOR TO THE AREA OF REDUCED VISIBILITY -- SHOULD IT OCCUR. IN ANY CASE, THE RVR VISIBILITY WAS WITHIN NORMAL LIMITS. I ASSUMED THAT WE WOULD HAVE SUFFICIENT VISIBILITY. THE FO WAS FLYING THE ACFT AND DOING FINE. WE DID ENCOUNTER THE RAIN. THE DOWNPOUR, HOWEVER, WAS TORRENTIAL AND WHILE THE RVR MAY HAVE BEEN 2000 FT, DUE TO THE HUGE AMOUNT OF RAIN ON THE WINDSHIELD, MY ABILITY TO SEE OUTSIDE OF THE COCKPIT WAS OBSCURED COMPLETELY EXCEPT FOR VERY SHORT GLIMPSES NEAR WHERE THE WIPER (AT THE HIGHEST SPD) HAD JUST SWEPT. I TOOK CTL OF THE ACFT DURING THE ROLLOUT, WHICH WAS UNEVENTFUL. MY CONCERN IS THAT IN HVY DOWNPOURS, THE STATED RVR DOES NOT TELL THE STORY OF ACTUAL VISIBILITY FROM THE COCKPIT AND IN THIS CASE, I WAS SERIOUSLY CONCERNED THAT I COULDN'T SEE THE RWY, DESPITE WHAT ONE WOULD BE LED TO BELIEVE WAS ADEQUATE VISIBILITY. I'D LIKE TO THANK THOSE RESPONSIBLE FOR THE HUD -- WHICH LIKELY SAVED OUR BACON. PLTS FLYING A NON-HUD AIRPLANE WOULD HAVE BEEN GROPING BLIND TO FIND THE RWY. I BELIEVE THAT WE SHOULD INVESTIGATE, PERIODICALLY, APPLYING A COMPOUND SIMILAR TO THE PRODUCT 'RAIN-X' TO OUR FORWARD WINDSHIELDS. THIS PRODUCT CAUSES THE WATER TO SHEET AND IS MUCH MORE EFFECTIVE THAN WIPERS -- NO MATTER HOW FAST THEY ARE BEATING. I DO NOT KNOW HOW DIFFICULT OR EXPENSIVE IT WOULD BE TO DO SO FOR THE ENTIRE FLEET. I DO KNOW THAT WE WOULD HAVE BEEN IN JEOPARDY OF DEPARTING THE RWY IN A NON-HUD AIRPLANE, AND I KNOW THAT WOULD HAVE BEEN EXPENSIVE. I KNOW THERE ARE THOSE THAT THINK WE HAVE DONE AWAY WITH 'RAIN REPELLENT' AND THE EXPENSE ASSOCIATED WITH IT. I THINK THE DISCUSSION NEEDS TO BE REOPENED. 'RAIN X' IS A VERY LOW VISCOSITY LIQUID APPLIED MONTHLY. HOW IT WOULD FARE IN THE TORTUROUS ENVIRONMENT OF HIGH SPDS AND TEMP EXTREMES, I DO NOT KNOW. RVR IS NOT ADEQUATE TO DESCRIBE VISIBILITY DURING A HVY DOWNPOUR. ANOTHER MEASURE NEEDS TO BE DEVELOPED TO ADEQUATELY DESCRIBE THE ABILITY OF THE PLT TO SEE THROUGH THE WINDSHIELD WHILE MOVING FORWARD AT 130 KTS. VISIBILITY RPTED BY TRANSMISSOMETERS OR OTHER STATIONARY OBSERVERS IS NOT ADEQUATE. COMPANY REPLY: THE TRANSMISSOMETERS MAY NOT BE POSITIONED TO GIVE THE PLT AN ACCURATE EVALUATION OF VISIBILITY ON THE RWY IN THESE TYPES OF DYNAMIC CONDITIONS. THEY'RE GREAT FOR PREDICTING WHAT YOU'LL GET IN A MORE HOMOGENEOUS PHENOMENON, LIKE FOG OR HAZE. FAST MOVING SQUALLS MAY NOT FALL INTO THEIR FIELD OF VIEW. CARE AND JUDGEMENT NEED TO BE EXERCISED IN THE VICINITY OF SQUALLS FOR A VARIETY OF REASONS INCLUDING DOWNDRAFTS AND WINDSHEARS. THE FOM HAS SOME GUIDANCE ON THIS AS WELL. AS FOR THE WINDSHIELDS, THEY COME FROM PPG WITH A HYD COATING ON THEM THAT WILL EVENTUALLY WEAR OFF. I AM NOT SURE RIGHT NOW WHETHER WE SPEND THE MONEY TO REAPPLY THE COATING. I'LL FIND OUT ASAP AND LET YOU KNOW. AS FOR THE HUD, IT CONTINUES TO PAY FOR ITSELF TENFOLD ON OCCASIONS SUCH AS THESE. AS PART OF THE CERTIFICATION, NUMEROUS LNDGS IN THE ACFT WERE PERFORMED WITH CARDBOARD COVERING THE ENTIRE CAPT'S FORWARD WINDSCREEN, ESSENTIALLY 0/0, WITH PERFECT TOUCHDOWNS AND ROLLOUTS, SIMILAR TO OUR LNDG. WE ARE A LUCKY FLEET TO HAVE THIS PWRFUL DEVICE.

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.