Introduction of Global Reporting Format: Summary of the First Winter Season in Poland

Abstract

Over the years, Global Reporting Format (GRF) was the first major change in the approach to evaluate runway conditions. The greatest impulse for this new regulation were incidents and accidents related mainly to runway excursions that occurred because of unfavorable weather conditions, when not only aircraft and different airport facilities but also human health and lives suffered. To better understand these changes, their advantages and their disadvantages, as well as the challenges that arose, an expert survey was carried out with duty officers of Polish airports, who directly made an assessment of runway conditions. Beside strengths of the GRF approach, research results show its weaknesses and uncertainties, especially when using the Runway Condition Assessment Matrix. In addition, in the article are presented a brief GRF description together with comparison with the previous reporting system and a discussion about air accident statistics related to a runway excursion, as well as a description and discussion of one selected air incident that took place in Poland.

1. Introduction

Weather conditions in the winter season have a particular influence on aviation. The air transport system consists in general of passengers and freight on the one side, air carriers, their networks of connections and fleet on the other side and, additionally, airports and their infrastructure facilities to link them all together. Each of these elements feels the effects of winter weather very painfully: passengers are late to reach the final destination or connecting flights and consignors get contract penalties for delays of freights. To meet the expectations of their customers and, at the same time, maintain an appropriate balance between costs and safety, air carriers and airport operators implement special procedures.

Most people believe wrongly that the landing process is complete when aircraft wheels touch a runway surface and that the culmination of a safe landing is the start of speed loss by the aircraft. Unfortunately, this is not so, which is confirmed by the accident statistics on runways [1]. They were arising not only because of human factor or delicacy of aircraft design, but also to the fact that during landing and takeoff phases there is a change in the way of movement from flying to rolling and from rolling to flying, respectively. Here it should be noted that weather conditions are playing a very important role for both these stages, especially during the winter season.

The Southwest Airlines Flight 1248 accident—a runway overrun—in 2005 took place at the Chicago-Midway Airport (MDW/KMDW) [2]. During the investigation, it was believed that its main cause was human error, while there were also inconsistencies when providing information about the prevailing weather conditions. This was one of the main impulses for why the Federal Aviation Administration (FAA) established the Takeoff and Landing Performance Assessment Aviation Rulemaking Committee (TALPA ARC) in 2007 [3]. This committee started to develop standards and recommendations to increase the safety of air operations on wet or contaminated runways. In 2008, work in this area was also started by the International Civil Aviation Organization (ICAO) within the scope of the Friction Task Force. All this work gave rise to the creation of the Global Reporting Format (GRF) regulations introduced in 2021.

The main purpose of this study is to summarize and analyze advantages and disadvantages of the GRF introduction, which started to be clear after the winter season when this approach was first implemented to assess runway conditions. An expert survey was used as a research tool. Airport operational staff represented by duty officers of Polish airports were selected as experts because they are the personnel who directly estimate runway conditions. The best of our knowledge, it is the first such research study done in Poland, as well as in the European Union. Additionally, such supporting aspects as changes in the procedures of runway condition assessment, as well as the problematics of runway excursions, are described. The discussion about runway excursions as the main “outcomes” of wrong runway condition assessments or wrong adaptation to them is done to point out the importance of the GRF approach and its appropriate implementation. Accident statistics are presented to estimate indirectly the effect of GRF introduction. Finally, the considered case study shows how harsh weather conditions could lead to undesirable consequences, even when all procedures are followed correctly.

2. Influence of Weather Conditions on Runway Excursions

It should be remembered that, besides financial and image losses, the most negative consequences of incidents and accidents in transport are human victims. Runway overruns are associated with three main causes, one of which is unfavorable weather conditions [4]. According to the data collected in 2003–2010 by Boeing [5], there is no single cause for runway excursions, which are also divided into two types: veer-offs (off-side runway excursions) and overruns (off-end runway excursions). Here, the landing was divided into three stages: approach–touchdown–deceleration. From the data collected by the American manufacturer, the runway condition was other than dry in 90% of the considered runway excursion cases. According to the adopted division, the state of a runway is the most important in the deceleration phase. Obviously, the reduced friction is not the only one factor contributing to runway excursions; it is usually a sequence of undesirable events, starting from technical aspects, through procedures, to the human factor.

Statistics on aviation incidents and accidents are collected in many countries all over the world. Research work conducted by Jacobs Consultancy for Transport Canada in 1990–2007 pointed out that the risk of a runway excursion is seven times higher if the state of a runway surface is other than dry. The data review showed that the majority of runway excursions associated with jet aircrafts, for which 37% of cases happened on wet runways, as well as in 52% of cases when runways were contaminated with residual sediments [6]. In 2014, the European Union Aviation Safety Agency (EASA) also presented information that 36.3% of runway excursions when landing were on wet and/or contaminated surfaces [7]. All of these confirm that the runway state should be identified as a significant safety contributor. On the other hand, investigations after aviation accidents have repeatedly confirmed the lack or incompleteness of information about the type of contamination.

The Accident Investigation Board Norway (AIBN) presented a report in which 30 undesired events were analyzed [8]. As a result, it was shown that aircraft braking coefficients (ABC) are not adequate to the measured/estimated runway friction coefficients (FC). The AIBN determined that it was influenced by meteorological conditions and uncertainty of measurement, as well as operational and regulatory aspects. This study compared FC values with ABC values: only a moderate correlation of around 0.5 for measurements on dry surfaces was found; there is no correlation for compacted snow or ice or for other known contaminants.

3. Methods to Assess Runway Conditions

3.1. State before GRF Introduction

First of all, it should be noted that before the introduction of the GRF there was a large discrepancy in the way ground services in different countries provided and reported necessary information about runway conditions. When referring to the experience in Poland, it should be said that all procedures are based on Annex 15 of the ICAO Convention [9]. Braking information was provided by Air Traffic Control (ATC) units according to the ICAO scale; estimates were given for each third of a runway in plain text. In the landing instructions (LDG), runway thirds were marked as FIRST/SECOND/THIRD starting from the lowest runway threshold. Information on snow conditions at airports was published using a special NOTAM series (SNOWTAM) in accordance with the ICAO SNOWTAM format contained in the same ICAO Annex. When summarizing experiences of other countries, the main differences in the way to report runway conditions concerned [10]:

• References to runway thirds,
• Used formats,
• Scopes and ways to transfer the same information to the ATC.

Before the GRF introduction, ground friction measurement devices were widely used to determine friction coefficients and, consequently, to assess braking parameters. There is a large number of such tools available on the market and used by airport operators. Measured values from these devices were much too often a main base in the different methods applied to assess the runway conditions before the GRF. It should be noted that not every device can be applied in all conditions: there are different guidelines concerning this issue; for example, the US Department of Transportation provided its own Advisory Circular [11].

As written above, prior to the GRF introduction, a five-point runway condition assessment scale of the ICAO Annex 15 was in force and, consequently, was associated with appropriate friction coefficient.

Table 1. Comparison of friction coefficients with aircraft braking performance.

Estimated Surface Friction		Measured or Calculated Friction Coefficient (a)	Airplane Braking Coefficient (b)
5	good	0.4 and above	μB > 0.20
4	medium/good	0.39 to 0.36	0.15 < μB ≤ 0.20
3	medium	0.35 to 0.30	0.10 < μB ≤ 0.15
2	medium/poor	0.29 to 0.26	0.075 < μB ≤ 0.10
1	poor	0.25 and below	0.05 < μB ≤ 0.075
9	unreliable	-	μB ≤ 0.05

^(a) based ICAO scale according to Annex 15 Appendix 2 [9]; ^(b) based on Klein-Paste et al., 2012 [12].

shows the comparison of these values with the braking performance of aircraft, which was measured on contaminated runways during winter [12]—the differences are obvious.

Unfortunately, the devices are also not universal, in the first instance because they return appropriately correct results only for certain types of contaminants. The most frequent arguments against measuring devices as being far from the braking parameters of airplanes are:

• Measuring wheel size,
• Measuring wheel load,
• Measuring wheel air pressure,
• Speed,
• Slip ratio,
• Drag,
• Uncertainty of measurements under specific weather conditions.

Klein-Paste with co-authors in 2015 [13] provided quite a clear explanation of the challenges, which do not allow the consideration of results from measuring devices as finally correct and corresponding to the reality. It was pointed out that parameters such as speed, tire characteristics, load, braking and contact time vary widely between the measuring devices and the aircraft tires. When braking, the rotational speed of a tire is reduced in comparison with a slow-running tire, causing slippage. As the tire rolls and slides, the friction arises because of hysteresis in the rubber, which is deformed on the snow and/or ice, creating and changing points of contact. High slip speeds can be a reason for frictional melting. Such substances as water, slush and wet or dry snow must be pressed through the tire tread to obtain adequate friction. Summarizing, it was said that the complexity of the processes taking place during the contact of the tire with the ground and the number of factors affecting them makes it impossible to recreate at least similar processes during the measurement with a scaled measuring tire.

3.2. Approach of Global Reporting Format

As a result of different identified inaccuracies or erroneous assumptions, the GRF was developed after many years of joint international work. In the European Union countries, upcoming regulations were initially presented as a draft form much in advance of their planned introduction in 2020. The situation was complicated by the COVID-19 pandemic, which took all the world’s attention and stopped a lot of processes, especially in the field of air transport [14,15]. That is why the deadline of the entry of the GRF into service was postponed by one year. This “extra time” was used by many airport operators to provide simultaneous tests of both systems of runway conditions assessment, which guaranteed a smooth transfer between them. Additionally, it was an ideal period because the number of air operations was still low: any delays in the GRF procedure did not impact on the punctuality of air traffic.

The general idea to introduce GRF around the world was to make it a kind of standardized connection between aircraft manufacturers, air controllers, airport infrastructure managers and aircraft crews. The main reason was mentioned above: the previous method based on ground friction measurement devices was not accurate for real aircraft braking parameters.

Now, the airport operator assesses the runway surface conditions with particular attention to contamination, describing each runway third separately with all details (their type, depth and coverage extensity). To make it a bit easier, many airports applied the Runway Condition Assessment Matrix (RCAM) on paper or even in special mobile apps. Then the collected data is reported in the form of a Runway Condition Report (RCR) to the air traffic services (ATS). These services transmit this information further to end users (aircraft crews, airport operational control centers, etc.) via radio communication, the Automatic Terminal Information Service (ATIS) system and SNOWTAM messages. Crews use the obtained data to calculate the aircraft performance and influence indirectly on possible RCR corrections when reporting post-landing braking (aircraft reports, AIREP). It should be noted that SNOWTAM messages are issued also when the runway is wet, although this condition is not related to the presence of snow. Even if changes in runway conditions during the winter season occur much more often than during the summer one and, consequently, they seem to be very critical for safety of air operations, especially in the cold period of time, the GRF is a tool for use during the whole year: this is particularly evidenced by the inclusion in the type of coating, slippery wet, as an additional one to differ it from “ordinary” wet, which may be associated with the slipperiness caused by poor runway drainage or by rubber deposition. RCR is divided into two parts: the first one influences the configuration of aircraft parameters for flight and braking; the second one specifies conditions of the runway surface concerning situational awareness.

The core of RCR is a single-digit code corresponding to the runway condition—Runway Condition Code (RWY CC). It depends on:

• Air temperature,
• Type of contamination,
• Depth of contamination,
• Extensity of contamination.

Table 2. Assessment criteria according to GRF based on [16].

RWY CC	Runway Condition Description	Pilot-Reported Braking Action
6	Dry	-
5	Frost Wet (includes damp and 3 mm depth or less of water) Slush (3 mm depth or less) Dry Snow (3 mm depth or less) Wet Snow (3 mm depth or less)	Good
4	Compacted Snow (−15 °C and colder outside air temperature)	Good to Medium
3	Slippery When Wet (wet runway) Dry Snow or Wet Snow (any depth) over Compacted Snow Dry Snow (greater than 3 mm depth) Wet Snow (greater than 3 mm depth) Compacted Snow (warmer than −15 °C outside air temperature)	Medium
2	Water (greater than 3 mm depth) Slush (greater than 3 mm depth)	Medium to Poor
1	Ice	Poor
0	Wet Ice Slush over Ice Water over Compacted Snow Dry Snow or Wet Snow over Ice	Nil

presents the criteria used to establish RWY CC.

The new procedure to generate a runway code requires more input information than before. As mentioned above, the Runway Condition Code on the new scale depends on the type of pavement contamination. Based on conclusions from the investigated air accidents, developers of the new system paid special attention to a wet surface because the previous advisory materials in terms of landings on wet runways did not provide an adequate safety margin [17]. Generally, the number of contamination types has increased in comparison with previous guidelines.

Within the scope of GRF, RWY CC is established by using RCAM, which also includes procedures to lower or to increase the final single-digit code. RCAM is a tool for both airport operators and aircraft operators, where types of contamination and their depths are related directly to the aircraft performance.

An example of a typical RCR is shown in Figure 1 with all of the necessary explanations. The abbreviations and codes used in the GRF comply with ICAO Doc 8400 [18]. In addition, RCR can be provided with information, which allows the crew of landing aircraft to better understand the situation at the airport. This information may include also all kinds of runway parameter limitations or the state of taxiways or aprons (Figure 2).

The RCR presented above is a set of data that pilots see through different sorts of information distribution tools. However, before RCR becomes valid, an airport operator must provide all the necessary information on the SNOWTAM form. This form was already known before the introduction of GRF and has undergone the necessary changes to adapt to the larger amount of data. Additionally, the maximum validity time of a SNOWTAM message has also changed: this period has been reduced from 24 to 8 h. In addition, a new SNOWTAM message has to be issued with each RCR change. The reasons for such revisions were the analysis of aviation incidents and accidents, which showed that in a number of cases the information from SNOWTAM was out of date.

4. Runway Excursion

4.1. Overview of Selected Statistics

With the help of the Aviation Herald service (website avherlad.com accessed on 31 August 2022), runway excursions from the period October 2021–March 2022 were collected and presented in

Table 3. Weather-related runway excursions in October 2021–March 2022.

Date	Airport	Aircraft	Description and METAR Weather Reports
17.11.2021	SBMG	B738	Runway excursion
			SBMG 180300Z 35001KT 8000 -RA BKN020 BKN100 21/20 Q1011 RERA=
			SBMG 180200Z 15005KT 9999 VCTS FEW030 FEW030CB BKN100 21/20 Q1011=
24.11.2021	UOOO	SU95	Runway excursion
			UOOO 240300Z 15015MPS 6000 -SN BLSN NSC M11/M14 Q0992 R19/39//38 NOSIG RMK QFE728/0971=
			UOOO 240230Z 15014MPS 7000 -SN BLSN NSC M11/M14 Q0992 R19/39//38 NOSIG RMK QFE728/0971=
27.11.2021	EFVI	A319	Runway excursion
			EFIV 270650Z 22003KT 170V240 9999 -SHSN FEW015 BKN033 M20/M22 Q1007=
			EFIV 270620Z 23003KT 9999 -SHSN BKN039 M20/M22 Q1007=
30.11.2021	YBBN	B773	Runway excursion
			YBBN 301130Z 34007KT 3000 +RA BKN006 BKN010 22/21 Q1013=
			YBBN 301119Z 07006KT 020V100 3000 +RA BKN006 BKN010 22/22 Q1013=
01.12.2021	USCC	CRJ2	Runway excursion
			USCC 302200Z 17007MPS 9999 -FZRA SCT030 M01/M04 Q1006 R09/350235 NOSIG RMK QFE734=
			USCC 302130Z 17008MPS 9999 -FZRA SCT030 M01/M04 Q1006 R09/350235 NOSIG RMK QFE734=
03.12.2021	EVRA	BCS3	Runway excursion during turn into taxiway
			EVRA 031020Z 28006KT 220V350 0750 0500 R36/1300U +SN BKN005 OVC010 M02/M03 Q0993 TEMPO 2000 SN=
			EVRA 030950Z 28004KT 210V340 0750 0650 R36/1300N +SN BKN005 OVC009 M02/M03 Q0993 TEMPO 2000 SN=
10.12.2021	RPVM	DH8D	Runway excursion
			RPVM 100400Z 36012KT 9999 -RA SCT020 OVC090 26/22 Q1011 RMK A2985=
			RPVM 100300Z 01015KT 9999 -RA SCT020 OVC100 28/23 Q1011 RMK A2985=
11.12.2021	EFHK	A359	Runway excursion during runway line-up
			EFHK 110120Z 10011KT 9999 OVC004 M01/M01 Q1016 NOSIG=
			EFHK 110050Z 10012KT 9999 OVC004 M01/M01 Q1016 TEMPO BKN005=
07.01.2022	KJHW	SW4	Runway excursion
			KJHW 070932Z AUTO 24010KT 4SM -SN BR BKN013 OVC019 M08/M09 A2981 RMK AO2 P0000 FZRANO=
			KJHW 070856Z AUTO 25012KT 5SM -SN BR OVC015 M07/M09 A2981 RMK AO2 SLP125 P0000 60,000 T10721094 50,007 FZRANO=
17.01.2022	LRCL	A320	Runway excursion during backtrack
			LRCL 172200Z 29015G25KT CAVOK M01/M05 Q1017=
			LRCL 172130Z 30017KT CAVOK M01/M05 Q1017=
21.01.2022	KRDU	CRJ9	Runway excursion during left turn into taxiway
			KRDU 220208Z 03004KT 1 1/2SM -SN BR FEW010 OVC020 M04/M06 A3039 RMK AO2 P0001 T10441061=
			KRDU 220151Z 03008KT 2SM -SN BR FEWO1 M0309/LP29K02 T10441061=
16.02.2022	SBRF	B738	Excursion from the runway and destruction of runway edge lamps
			SBRF 170300Z 12005KT 090V150 8000 VCSH BKN017 SCT050 25/23 Q1012=
			SBRF 170200Z 09005KT 030V120 9999 SCT022 BKN100 28/23 Q1013=
08.03.2022	UUWW	B735	Runway excursion after aborted take-off stop in snowbank
			UUWW 080000Z 36005MPS 2100 -SHSN BKN005 BKN020CB M04/M07 Q1010 RESHSN R06/590535 TEMPO 0600 +SHSN BKN012CB=
			UUWW 072330Z 36004G09MPS 330V040 1200 0800SE R06/P2000U +SHSN BKN007 BKN020CB M04/M06 Q1010 R06/590535 TEMPO 0600 +SHSN BKN012CB=

. METAR messages were added to each event with the aim to better illustrate the meteorological situation at certain airports.

First, it should be mentioned that there were 13 accidents in the winter season 2021–2022 counted by the Aviation Herald. Taking into account the COVID-19 pandemic, which restricted air transport traffic globally [19,20], the winter season 2018–2019 as the last pre-pandemic one was chosen to make a comparison. For the same period from October 2018 till March 2019, the service registered only seven accidents involving runway excursions. Although the reliability of the data is relatively weak and it is impossible to make any detailed statistical analysis, this information confirms that at present there is no evidence of any positive changes after the GRF introduction. Here, it should also be pointed out that the direct comparative analysis between METAR and RCR is quite problematic because of two reasons: (1) METAR is issued a minimum of one time per hour, while RCR is produced depending on the needs; (2) although RCR does not contain any secret information, it is not publicly available as opposed to METAR (part of the data can be extracted only from SNOWTAM). That is why such an analysis is beyond the scope of this article.

Second, it is worth emphasizing once again that accidents in air transport rarely happen for only one reason—usually it is a sequence of events [21]. For runway excursions, runway contamination reducing friction and wind strength and direction are the key factors, which are influenced by weather conditions. This thesis is confirmed by the data from Table 2. Most of the presented METAR messages contain information about precipitation—snow (SN), freezing rain (FZRA) or “ordinary” rain (RA)—and the accompanying wind with varying strength and direction in relation to the runway. Naturally, runway excursions will logically be the most common problem for airports located in areas prone to snow and heavy rainfall. However, taking into account climate changes, such types of accidents on the runway can occur anywhere. It should be underlined again that runway excursion issues do not concern only landings. As shown in Table 2, these types of events also occur during other actions and situations, such as execution of ground maneuvers, rejected take-offs or runway line-ups.

4.2. Case Study of Incident at Katowice Wojciech Korfanty Airport

As mentioned above, data reliability of such services as the Aviation Herald is quite weak because they do not immediately include all incidents and accidents that happen. One of the main reasons is bureaucracy: according to a standard procedure, which is quite similar in all countries, each accident should be registered and described by a special commission, which takes some time. In addition, it should be mentioned that incidents are investigated only in very special cases; most often they are only registered without any further reporting.

Here, we would like to present and to discuss briefly the incident that happened in the winter season 2021/2022, which was registered by the State Commission on Aircraft Accidents Investigation (SCAAI; in Polish: Państwowa Komisja Badania Wypadków Lotniczych, PKBWL). As it was only an incident, an investigation was not done and, consequently, there was no official report issued, but, on the other hand, this undesirable event was heavily publicized in the media and on social networks. To prepare this description, besides open-source data, the radio communication between all parties involved in this case was analyzed.

On 1 February 2022 around 11:57 PM UTC (local date and time: on 2 February 2022 around 00:57 AM CET), at Katowice Wojciech Korfanty Airport (EPKT), a Boeing 737–800 with registration number SP-RSB fell off runway RWY27 when turning into taxiway TWY L. The aircraft was Ryanair flight RYR1DT from the Cologne Bonn Airport (EDDK) to EPKT. As pointed out above, for obvious reasons there was and will be no official reporting by SCAAI, but there is no doubt that the role of the conditions on the runway was certainly significant. The aircraft was approaching the airport when it received information about a snow removal operation on the runway, which was associated with a 15 min delay. The crew got the RWY CC from approach control: it indicated 3/3/3 and a 100% wet snow cover (these data came from SNOWTAM; the original RCR was not available). Interestingly, when the SP-RSB aircraft was going straight in to RWY27, a crew of another aircraft was informed by the EPKT tower controller about heavy snowfall, as well as visibility of the touchdown zone (TDZ) and runway visual range (RVR)—1200 m and more than 2000 m, respectively. After being stabilized to RWY27, the Ryanair aircraft landed and, according to instructions from the controller, had to leave the runway using TWY L. The crew confirmed that instructions were received, but, after several dozen seconds after landing, reported to the controller the necessity to use a tug because TWY L had been missed: the place of this incident was marked with a red square in Figure 3. Taking into account the above-presented description, it could be assumed that runway conditions should be given as a reason for why the aircraft passed the taxiway. It could be confirmed also when looking at METAR weather reports, which show that a snowfall of varying intensity was continuing for a long time before and after the incident (

Table 4. Weather conditions when the considered incident took place.

Local Date	Local Time	METAR Weather Reports
01.02.2022	21:00	EPKT 012000Z 21015KT 4300 -SN BR FEW010 BKN021 BKN024 00/M01 Q0999 RESN=
01.02.2022	21:30	EPKT 012030Z 21015KT 1500 +SN BR FEW002 SCT005 BKN010 M00/M01 Q0999=
01.02.2022	22:00	EPKT 012100Z 21014KT 0500 R27/1600N +SN SCT002 BKN006 OVC007 M00/M01 Q0998=
01.02.2022	22:30	EPKT 012130Z 21014KT 1800 SN BR BKN002 OVC005 M00/M01 Q0997 RESN=
01.02.2022	23:00	EPKT 012200Z 22013KT 2000 SN BR SCT002 BKN003 BKN004 M00/M01 Q0997 RESN=
01.02.2022	23:30	EPKT 012230Z 23014KT 1300 R27/1900 +SN BR BKN002 OVC004 00/M00 Q0997=
02.02.2022	00:00	EPKT 012300Z 22015KT 1400 R27/1700 +SN BR SCT001 SCT003 OVC004 00/M00 Q0996=
02.02.2022	00:30	EPKT 012330Z 22014KT 1200 R27/1800N SN BR BKN002 OVC005 00/M00 Q0996 RESN=
02.02.2022	01:00	EPKT 020000Z 24014KT 8000 -SN SCT003 OVC004 00/M00 Q0996 RESN=
02.02.2022	01:30	EPKT 020030Z 22012KT 1800 +SN BR BKN002 OVC004 00/M00 Q0996=
02.02.2022	02:00	EPKT 020100Z 23014KT 5000 -SN BR SCT002 OVC003 00/M00 Q0996 RESN=

).

When the above-presented situation arose, near the EPKT airport only one aircraft was waiting to land; a few minutes later another airplane joined the queue. Meanwhile, the aircraft SP-RSB had been immobilized and was waiting for a pushback vehicle. Because it was impossible to determine precisely the time required to push the airplane out, pilots of the held aircrafts decided to land at alternate airports. While initially the runway closure time was estimated at 20 min, then at 60 min, the EPKT runway was finally unblocked after 5 h. In the meantime, the EPKT airport duty officer requested the publication of a NOTAM concerning the runway closure:

H0184/22 NOTAMN

Q) EPWW/QMRLC/IV/NBO/A/000/999/5028N01905E005

A) EPKT

B) 2202012350

C) 2202020100 EST

E) RWY 09/27 CLSD DUE TO TECR

This NOTAM confirms again the large influence of weather conditions on the airport operation, as well as the difficulty to make any precise estimations: the duty officer assumed that this problem could be solved over 1 h, but weather conditions did not allow to do it faster than 5 h. Finally, the aircraft SP-RSB was towed to a parking lot; nobody from six-person crew or the 102 passengers was hurt.

The whole situation was qualified by SCAAI as an incident, which does not require any further reporting. However, putting aside any speculation, whether it was a fault of the aircraft crew when maneuvering or of the airport operator when preparing runway surface improperly, there is no doubt that harsh weather conditions contributed to the considered incident. Summarizing, this seems to the first case of a runway excursion in Poland after the GRF introduction. It is to be regretted that in Poland there are no official reports prepared and issued for incidents: in the presented case, such a report could have contained valuable information for both crews and airport operators to prevent such runway excursions in the future.

5. Results of Expert Survey

The winter season 2021/2022 was the first time when GRF was implemented everywhere. For sure, GRF application concerns not only the winter period but, particularly in Poland, this time of the year abounded in RCR reports. To understand more deeply the challenges associated with the GRF introduction and application, it was decided to conduct an expert survey among the staff of the airport operational services—the first persons who were obligated to use it. Taking into account the specifics of the management organization in Polish airports, the target group consisted only of duty officers, who are the main personnel working in the airside zone and making the necessary assessments of runway conditions.

An expert survey is a well-known research tool used in different scientific spheres including the transport field [22,23,24]. Opinions of experts are especially useful if they are required to understand new and/or difficult issues when available knowledge is limited. The number of invited experts varies strongly: from 4 to 247 persons [25]. It depends strongly on the selected research issue and, consequently, the availability of experts knowing this topic. That is why the usage of this technique was considered suitable for such a study. The estimated number of duty officers at Polish airports is approximately 100, out of which 21 participated in the administered expert survey. All of them were male, with ages from 30–56 years (average 41.2 years) and with experience of 4–27 years (average 9.8 years) working in airport operational services. Survey participants represented both the main airport—Warsaw Chopin Airport—and regional airports such as Kraków John Paul II International Airport, Gdańsk Lech Wałęsa Airport and Olsztyn-Mazury Airport. The survey was done in the form of a questionnaire, which was carried out in August–September 2022 and included both multiple-choice questions and open questions, allowing the expression of opinions and the giving of feedback about the research issue.

5.1. Advantages of GRF Implementation

According to experts’ opinions, the first days after GRF started to be obligatory could be considered an adaptation period when the whole system seemed to be complicated and not entirely easy to use. Very soon, all the fears passed and work with GRF started to be an everyday reality. When estimating the process of GRF introduction by using the Likert-type scale (1—very bad, 2—bad; 3—average; 4—good; 5—very good), it received 3.4 as an average grade: only three duty officers assessed this process as very bad or bad. Additionally, opinions about how the new procedure influenced the duration of the condition assessment activities are shared more or less equally: eight persons agreed that the process starts to be longer, seven experts did not see any difference and six respondents confirmed that GRR shortened the process.

Asking experts about the advantages of GRF introduction as an open question, it should be pointed out that, as the main advantage, 29% of respondents named the uniformity and the consistency of the assessment approach and outputs, as well as the reporting ways, for all users, which should minimize the possibility to make any individual interpretations when estimating runway conditions. Among other advantages were mentioned (1) the lack of the necessity to assess braking parameters with the help of ground friction measurement devices, (2) the increased number of surface contaminants types—71% of experts assessed this change on the level “good” or “very good” by using the same Likert-type scale as mentioned above, (3) the faster speed of information delivery because RWY CC is only a single-digit code for each runway third, and (4) the opportunity to make such assessments as frequently as needed. Additionally, in the opinions of some airport operational staff, the usage of RWY CC should theoretically make it easier for pilots to set an appropriate aircraft configuration before landing. However, 19% of experts concluded that they did not see any benefits from GRF introduction.

Interestingly, it was reported by some duty officers that they started to more often request the tower controller to ask the crews of landing aircraft for their braking assessment, and, vice versa, pilots also started to ask additionally about braking parameters. The aim of both of these actions is logical—to verify whether the performed estimate is adequate to the needs of the aircraft. However, on the other hand, it contradicts to some extent the above-declared advantages concerning pilots and the lack of obligatory measurements. In addition, half of the experts confirmed the usage of measurement devices so far, although they mentioned the sporadic character of such actions, especially when uncertain situations arose. Importantly, according to the tests carried out, it was reported by 60% of these duty officers that the measured values often differed from those reported by the crews. This issue requires additional research to establish its character: whether it is temporary or permanent; however, such a study is outside of the scope of this article.

5.2. GRF Weaknesses and Uncertainties to Be Improved

First, it should be mentioned that 19% of the experts did not confirm any disadvantages of GRF when answering an open question about problems and, contrariwise, one person declared that the whole new approach has to be revised and improved in each element.

The whole GRF procedure could be divided nominally into three stages—data collection, data processing and data distribution—each of which was estimated by experts together and separately as well as was minimum one time mentioned to be a disadvantage in the open question. During the general estimation, 52% of duty officers mentioned the second phase—data processing—as the most problematic one. It was confirmed also by detailed assessment when the first, the second and the third stages got 57%, 43% and 76% of “good” and “very good” grades, respectively. This fact pointed out the complexity of the GRF approach by working with already collected data. On the other hand, it is impossible to forget about the challenges during the first and third phases. For example, no uniform electronic application to support the data collection was proposed, especially during critical situations when conditions are changing rapidly. Some airports are still working on paper documents; another tried to find a solution on their own using the services of external IT companies. The so-called “childhood diseases” of the data distribution stage could be considered the defects of the software that was initially used by the NOTAM office. The problem was that airport personnel repeatedly refused to publish SNOWTAM after supplying the necessary data. The reason was the inability to enter the following information by the NOTAM Office: RWY CC 6 with the type of pollution and the extent of 10–25% (Figure 4). Until the error was corrected, the NOTAM office added an appropriate note in SNOWTAM messages as a plain text.

Looking at the answers to an open question regarding the need for GRF improvement, 52% of the experts pointed directly or indirectly at RCAM. That is why, for the aim of this study, the usage of RCAM was divided into five elements: (1) contamination depth measurement, (2) outside air temperature (OAT) check, (3) identification of contaminant type, (4) identification of contaminant coverage percentage, (5) matching the collected data with RWY CC and (6) RCR creation. Each respondent estimated with the help of the Likert-type scale (1—without problems, 2—slight problems, 3—moderate problems, 4—significant problems, 5—serious problems) how each mentioned element is problematic to realize. Results of this assessment are shown in Figure 5.

Figure 5 shows that such actions as identification of contaminant type and contamination depth measurement are the most problematic ones. These RCAM elements got the highest grades with values of 2.6 and 3.5, respectively. Both of them were mentioned by experts when answering an open question about the need for GRF improvement. For example, it was proposed to add the value “damp” as an additional contaminant type. In addition, duty officers complained about the lack of standardized methods and/or tools to evaluate contamination depth, which could essentially reduce the measurement time, especially in cases of long runways.

Although the rest of the RCAM elements were assessed quite equally, attention should be paid to matching the collected data with RWY CC. Some of the duty officers were worried that sometimes runway conditions may differ significantly from those, which are encoded by the GRF assessment criteria. Of course, such situations may create unnecessary confusion, but taking into account experts’ grading it seems that they arose rarely. To the same RCAM element refers also a controversial issue when upgrade and downgrade of braking parameters could/should be done. Unfortunately, there are no special instructions on this. Pointing out this problem, experts declared that only the experience of airport operational staff and/or the usage of ground friction measurement devices could support making correct decisions.

An additional disadvantage is the longer occupancy of a radio channel, which is used to transmit current conditions directly from the runway. Taking into account the division into runway thirds, as well as classifications of type, depth and extent of coverage, the amount of transferred data starts to be very large. As a consequence, it requires more attention from controllers: besides the contact with services, which restore proper conditions of the runway surface, there are also crews of aircraft on a separate channel. Additionally, it is necessary to emphasize from which direction the message is conveyed. On the one hand, a person who performs an assessment and creates RCR is obliged to submit the data in the order from the lower values of the runway threshold value. On the other hand, the ATIS system, where these data are entered, was constructed in another way—always from the active landing direction. It is worth noting that the ATIS system is not operated by controllers at all airports. In some cases, it is the responsibility of the airport operation services. There is no doubt that the occupancy time of radio channels should come back during further discussion about the communications of ground services using the tower frequency, which is beyond the scope of this study.

Finally, it was mentioned that not all pilots are familiar with the GFR approach yet, but such cases could be mainly considered as exceptions—they will disappear as soon as the new system is completely rooted in the everyday life of air transport.

6. Discussion

Means of air transport are very susceptible to any impacts, among other things because of changes in the ways of movement, as well as in the environmental conditions, in which they are located. The high speed of movement combined with a large amount of fuel and the complicated structure design make their margin of safety relatively small. Notwithstanding that aviation is the branch of transport most described by various regulations, not all issues can be addressed in procedures, especially those characterized by high dynamics of variables, which are very common only locally. A perfect example here is the effect of weather conditions on an aircraft and on a runway on which take-off and landing operations are performed.

The importance of weather and runway conditions is again confirmed by Chang and co-authors in the research work about risk factors associated with pilots in runway excursions [26]. Among the general selection of preliminary risk factors, there are (1) the ability to apply the In-Flight Landing Performance Assessment, (2) the lack of the latest runway condition, weather change information and braking action conditions from ATCs, (3) wet/contaminated runways and (4) weather information availability and accuracy. It should be highlighted here that factor (3) was ranked as a top risk factor according to the pilot’s survey.

The GRF is the next attempt to develop a universal and optimal method that allows the obtaining and provision of the best possible information on runway conditions. On the one hand, it was implemented to increase the level of flight safety when it is being properly applied by aviation personnel. On the other hand, solutions based on the technique, such as a braking measurement, have been replaced by the experience of persons who work with the GRF creating RCR: staff “on the front line” who assess conditions on a runway in the field.

Results of this study show that, besides advantages like the uniformity and the consistency of assessment approach and outcomes reporting, there are still a number of aspects that require improvement. First of all, it concerns the work with RCAM. A separate issue for further discussion is the usage of measurement devices. They are still applied to confirm estimates made and are considered to be among the factors influencing their correction, although according to the GRF idea they had to be eliminated when assessing runway conditions and can serve only as a support.

7. Conclusions

The number of studies carried out over many years shows the inconsistency of values obtained by ground friction measurement devices with the real braking parameters of aircraft. In response to this discrepancy, the GRF was introduced. On the one hand, there were no major comments noticed from the pilots about the new system. Therefore, it should be understood that the GRF idea meets the needs on this side. On the other hand, this situation looks different from the viewpoint of airport operational staff responsible for maintaining the airport, especially during the winter season. An expert survey done one year after the GRF introduction showed its main difficulties and problems. It seems that without a proper intervention, a human factor will highly likely increase these problems: for example, errors could occur because of the over-/underestimation of RWY CC or the omission of difficult and/or unclear GRF stages by runway condition assessments.

Thus, results of this research work could be useful for all levels of the aviation authorities. At the level of airport administration, they allow them to understand deeper the challenges faced by airport operational services associated with the GRF introduction. At the level of different international aviation organizations, these outcomes could be considered as a background for further discussions on how the GRF procedure could be clarified, corrected and upgraded.

Certainly, the air transport industry will never completely eliminate undesired events, but their number could decrease. One of the ways is to evaluate in detail new regulations and procedures before and after their introduction, with the aim of eliminating their disadvantages.