I was wondering, are there any products (or could there be feasible) that would more dynamically give a runway surface friction measurement? The spatial non-uniformity of surface must also be a factor, so not an easy task I guess. But wondering what's out there and would it help?
Ah, some kind of semi-intelligent device which monitors the braking action vs what experience says the aircraft should be able to achieve, and which then by radio informs the tower of the result?
I think I've seen that somewhere. In fact, I recall there being two of said device, for reduncancy... and in order to let one system communicate with the tower while the other was busy getting the approach charts back in the binder.
"... Runway excursions ... attributed to quickly changing surface friction conditions on the runway.... are there any products ... that would more dynamically give a runway surface friction measurement? ... what's out there ..."
Faa says that they are still "considering" or working that project. Recall the recommendation A-07-64:
Date: October 4, 2007 NTSB Safety Recommendation: A-07-64 TO THE FEDERAL AVIATION ADMINISTRATION:
Demonstrate the technical and operational feasibility of outfitting transport-category airplanes with equipment and procedures required to routinely calculate, record, and convey the airplane braking ability required and/or available to slow or stop the airplane during the landing roll. If feasible, require operators of transport-category airplanes to incorporate use of such equipment and related procedures into their operations.
Response Date: 1/8/2008 From: Addressee [FAA] ... Letter Mail Controlled 1/14/2008 3:39:36 PM MC# 2080007: From Robert A. Sturgell, Acting Administrator, FAA, 1/8/08
... For A-07-64: The FAA agrees that, if feasible and cost effective, an airplane-based means for obtaining information on the runway surface condition, determining the available braking capability, and communicating that information to subsequent landing airplanes could be beneficial for operations in inclement weather. The FAA is considering a research project to examine the operational and technical feasibility of such a system. We will provide a more detailed response on this in 180 days.
From: NTSB
1/31/2011
... the NTSB requests that the FAA document the specific actions taken to address Safety Recommendations A-07... -64. Pending our receipt and review of this information, and the FAA's prompt action Safety Recommendation A-07-... -64 ... remain classified OPEN – ACCEPTABLE RESPONSE.
At TBC, during testing for RTO's and Lndg performance, the responsible engineers are ON BOARD the test aircraft (most of the time). For such runway STOPPING performance, the systems- engineers were from Landing Gear and Brakes group: After any performance landing, within seconds, these guys had the surface-friction data available. [Even a mist in the air affects this "mu", the tire-runway interface is complicated by that moisture.]
But think about a line-pilot landing: mostly we don't use the brakes as much as DRAG and ThRevrs. So, this aircraft-based rwy-friction measurement gets fouled by pilot-choice (easy-braking, Thrust Reverser application, &ct).
= = = / / = = =
EDIT -- this topic was discussed THREE DECADES AGO,
Recommendation Letter A-82-152 through -169, dated Dec'23rd, 1982, pg 5
The Safety Board believes that immediate action should be taken by the FAA to convene an industry-government group to develop standardized terminology and criteria for pilot braking reports ...
... Safety Board believes that the NASA and FAA programs should be broadened to determine whether existing systems on an airplane can be redesigned or modified to present quantitative indications of effective braking coefficients to flightcrews. For example, antiskid system modulating pressures or cycling frequencies might be used in conjunction with prescribed pilot braking techniques to calculate and display a quantitative braking coefficient. Also, the potential for using inertial navigation systems to measure deceleration and to provide a quantitative braking coefficient for those airplanes so configured should be explored. Such quantitive pilot reports would allow airport management to monitor deteriorating runway conditions more closely.
The FAA should also address the problems of communicating essential runway surface information to pilots. The existing two principal methods of relaying information to pilots are ATIS and individual controller reports. The Board has found that, for various reasons, these methods sometime are not effective, particularly in heavy workload situations....
... Safety Board recommends that the Federal Aviation Administration:
In coordination with the National Aeronautics and Space Administration, expand the current research program to evaluate runway friction measuring devices which correlate friction measurements with airplane stopping performance to examine the use of airplane systems such as antiskid brake and inertial navigation systems to calculate and display in the cockpit measurements of actual effective braking coefficients attained. ... (Rec' 8-82-168)
The Federal Aviation Administration (FAA) has completed its review of Safety RecommendationA-82-168 which is basically directed at using onboard aircraft systems to calculate ... an effective braking coefficient(s) attained for stopping distance....
... The intent of this recommendation has been suggested many times in the past ... various research projects since 1970 ... None of these projects has produced data or results which reliably correlate aircraft performance to friction measuring devices in an acceptable fashion. The major problem with such an onboard display system is that it would encourage operations from a runway surface that could have a very low friction coefficient. The system, even if perfect, would only display the potential surface conditions after the airplane had landed or needed to stop, which the FAA believes is a reduction in safety. If the intent is to use a preceding airplane to advise a subsequent airplane of the potential runway friction coefficient, this too would potentially degrade safety since the capabilities of different type aircraft do not necessarily relate to each other. Currently , a pilot advises ... surface braking conditions ... to plan subsequent operations on the particular runway. I plan no further action on this recommendation.
There is always the question of whether the measured friction is applicable only to the specific combination of aircraft, tires and brakes used, and the possible combinations thereof, or whether it is useful to other aircraft.
Would it be possible to have onboard systems measure it, and then relay it to ATC?
ABSOLUTELY! Use the human side of the human-machine interface!
Most experienced pilots can tell when the antiskid cycles the brakes, and can detect the minor swerving when one side of the runway is slipperier than the other. Tell Tower or Ground where you experienced the most active antiskid cycling, so they can take care of it AND advise others.
ross, I cannot recall any aircraft/system having a light indicating operation (anti-skid activity). Anti-skid can cycle the brake pressure very rapidly on wet and dry runways; see http://www.faa.gov/aircraft/draft_do...airAC25_7C.pdf page 55 onwards. Thus an activity indication may be meaningless or not even feasible.
I suspect you are thinking of an indication of the anti-skid system being available or not.
The problem with aircraft-based detection / analysis systems is that their output is historical – someone has to experience the conditions before a computation can be made; and even then the conditions can change quickly.
The ICAO guidance (thanks tribo), seeks to gather the highest quality of information to pass to a pilot before landing. Even at best, this information is only an estimate of ‘braking action’ (estimated surface friction).
It is interesting to note from the accident report (post #1) that the preceding aircraft (CRJ) reported having no braking problems. This could have been due to rapidly changing conditions or perhaps the CRJ’s use of reverse thrust. Reverse and auto-brake, can mask the actual braking condition (dependent on the source of decelerating force) because full brake effectiveness may not be demanded.
Any automatic assessment system would have to take account of this, but even so the result may only be an estimate for a particular aircraft type.
An automated system may reduce many of the risks arising from the use of PIREPS for guidance (highly subjective and type / operation specific), but in all instances where advanced information is not available, good judgement must be used – knowledge, awareness, risk assessment; how are these to be computed.
Realtime Runway Braking Action measurement
