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The following series of articles appeared this week online through AviationWeek.com
We have reposted them here since they present a very detailed analysis regarding several Phenom 100 landing accidents attributable to icing conditions. Links to the source articles are included in the re-posts below.
The author makes the point that "Lack of adherence to a warning or standard operating procedure (SOP) is not a training issue, but a compliance issue." We couldn't agree more.
Factors In Ice-Induced Hard Landings, Part 1
Roger Cox June 21, 2023
AviationWeek.com
We describe an EMB-500 hard landing in Paris and related incidents.
Author
Roger Cox
Content source
Business & Commercial Aviation
Primary Category
Safety, Ops & Regulation
https://aviationweek.com/business-aviation/safety-ops-regulation/factors-ice-induced-hard-landings-part-1
A charter crew approached Paris Le Bourget Airport in their Embraer EMB-500 Phenom 100 on the morning of Feb. 8, 2021. The wing and stabilizer de-icing system was not turned on when they passed through a layer of freezing clouds on final approach, and at 50 ft. above the runway, the airplane stalled. It descended rapidly and the recorders, FDR and CVR stopped when the airplane struck the runway. That happens when the G-load exceeds 5gs.
The crew did not forget to turn on the “Wingstab” de-icing system; they made a conscious decision to leave it off. Other Phenom pilots before them had made the same decision in similar circumstances, with the same results. One such accident took place in Germany in 2013 and another took place in the U.S. in 2014.
After those accidents, both the German BFU and the American NTSB made recommendations to prevent such accidents, but they weren’t entirely successful. The French Bureau d’Enquetes et d’Analyses (BEA) analyzed the Paris accident and came up with an additional insight that might be more helpful.
The accident flight departed Venice, Italy, at 0917 Paris local time and climbed to FL 340. The charter flight carried a two-pilot crew and one passenger. The co-pilot was the pilot flying. While enroute, the crew discussed the possibility of snow and a contaminated runway at Le Bourget and they tested the anti-icing system to ensure it was working. About 45 min. before landing, and before listening to the terminal information broadcast (ATIS), they briefed the normal clean-wing approach speeds. Those speeds were 97 kt. Vref, 102 kt. VAC (approach climb speed), and 121 kt. for VFS (final segment speed).
When they listened to the ATIS, it reported that the temperature was -1C (30F) and the dew point -3C and that there was severe icing between 3,000 ft. and 5,000 ft. The captain discounted this information, saying there was no snow and that icing was common near Le Bourget. The crew briefed the ILS approach to runway 27, planning to use full flaps and autopilot engaged. They did not consider any changes to the approach speeds.
Ten minutes before landing, the crew turned on the engine anti-icing and windshield demist/de-icing systems. As they intercepted the localizer, the crew activated the Wingstab de-icing system. Only 21 sec. later, after observing ice breaking off the wings, they turned that system off. They intercepted the glide slope, switched to the tower and were cleared to land on runway 27. They ran the before-landing checklist, and the captain turned off the engine anti-icing system.
The captain later stated that the cloud layer began just below 5,000 ft. and ended at 2,000 ft., and there was another thin layer at 1,500 ft. He did not see ice forming on the wing after he turned off the de-icing system.
At 300 ft. above the approach end of the runway, the airplane was stabilized at 100 kt. IAS and the autopilot was disengaged. Then the airplane began slowing and sinking, with the airspeed falling to 90 kt. and the angle-of-attack (AOA) increasing to 28 deg. The wings began to rock and the sink rate increased to 960 fpm. The captain, saying the airplane was too high on the glide slope, took control. The “STALL STALL” aural warning sounded and the captain attempted to advance power for a go-around. The airplane stalled in a 10-deg. right bank and landed hard.
The airplane came down only 33 ft. past the runway 27 displaced threshold and slid 3,445 ft. before veering off the left side of the runway and pivoting around to a heading of 160 deg. The nose gear broke off and the right main landing gear penetrated the right wing and the right fuel tank. A fire broke out near the wing root, but the occupants were able to safely evacuate the burning airplane. Aircraft Rescue and Fire Fighting Service (ARFF) responded and doused the fire.
Part 2: Clues to why the Phenom crashed.
Factors In Ice-Induced Hard Landings, Part 2
Roger Cox June 22, 2023
AviationWeek.com
Clues to why the Phenom crashed.
Author
Roger Cox
Content source
Business & Commercial Aviation
Primary Category
Safety, Ops & Regulation
https://aviationweek.com/business-aviation/safety-ops-regulation/factors-ice-induced-hard-landings-part-2
Paris-Le Bourget Airport (LFPB) has a tangle of runways, with the shortest being runway 27, at 6,060 ft. The airport is historic. It opened in 1919 and was the landing site for Charles Lindbergh after he first crossed the Atlantic Ocean solo in 1927. Coincidentally, it is also the home of the BEA. Investigators had only a short walk across the field to begin their examination of the wreckage of the Phenom. Upon their arrival, BEA investigators immediately noticed a build-up of ice along the leading edges of the wings and stabilizer.
After the initial visit to the accident site, the BEA organized the investigation according ICAO Annex 13. They brought in representatives from Brazil as the state of manufacture and Malta as the state of the operator. Brazil, in turn, brought in technical advisors from Embraer and Malta brought in advisors from Luxwing, the operator.
The investigation began with a focus on the design and operation of the airplane’s de-icing and anti-icing systems, the stall warning system (SWPS) and the airplane’s performance in icing conditions. The Phenom has three de-icing/anti-icing systems - thermal, for the engine intakes, electric, for the probes and windshield, and pneumatic, for the wing and stabilizer leading edges. The pneumatic system inflates and deflates leading-edge boots--four on the wings and two on the stabilizer. Some Phenoms are also equipped with an ice detector, but the accident airplane, 9H-FAM, was not.
The Embraer Phenom flight manual says that the Wingstab de-icing system must be turned on as soon as the total outside air temperature is less than 5C in the presence of visible moisture, even when there are no signs of ice accretion. A warning in the manual says “The ice protection system must be kept on until the crew is certain all ice has been removed.” When the de-icing system is switched on, the stall warning system and the low-speed awareness tape in the airspeed indicators adjust upward. The difference is significant.
For the conditions of the accident flight, the Vref speed without the de-icing system on was calculated to be 96 kt., but with the Wingstab and engine anti-icing system on, the calculated Vref was 119 kt.
The calculated landing distance for the accident flight was only 4,252 ft., flying at the lower Vref speed and leaving the anti-icing and de-icing systems off. With the equipment on, the calculated landing distance was 7,549 ft., which exceeded the length of runway 27. In addition, the one-engine-inoperative climb gradient was negative, meaning the airplane could not conduct a missed approach with the de-icing system on.
A review of the FDR showed that 3.8 nm from the airport at 1,380 ft, the flight was maintaining 135 kt. It had slowed to 100 kt. by the time it was at 468 ft. An Embraer simulation showed that the stall warning came very close to activating three times during the approach before it activated at the end of the flight.
The BEA interviewed the pilot of a Piaggio P180 who flew an approach to the airport about 10 min. before the Phenom. He said his visual ice-accretion probe accumulated so much ice that he took a photo of it. He provided that photo to the investigation, and it does indeed show a massive ice buildup on the probe.
The 40-year-old Phenom captain had logged 3,625 total flight hours, including 2,961 on the EMB-500. He had worked at the charter company for 8 years. The co-pilot, age 25, had logged 625 flight hours, including 425 in the EMB-500. His commercial license and EMB-500 type rating were less than a year old at the time of the accident. Both pilots had completed training on de-icing/anti-icing procedures and systems in the last year.
The captain said in a statement that he knew that the aircraft’s landing performance would not permit landing at Le Bourget Airport if the icing conditions on approach required the continuous use of the de-icing systems until landing. He said that after coming out of the cloud layer at 2,000 ft. he saw no more ice on the wings, so he deactivated the de-icing and anti-icing. He also said he knew he would have to divert if he left the de-icing system on.
The captain’s statement prompted the BEA to talk to other Phenom pilots and to review online Phenom pilot forums. One Phenom pilot said he had been unofficially taught that he could deactivate the de-icing systems after 1,000 ft. if the leading edges of the wings were not contaminated by ice. Another pilot, speaking anonymously on a forum, said “Frequently, in the Northeast, accompanied by bad weather and icing. Phenom book Vref increases when hots re on. For some reason Cessna does not have the same requirements. Spoke with one pilot who did a lot of 100 flying in cold wx. Said that as soon as he cleared the clouds on approach, would turn off the hots so that he could approach and land at normal speeds. Seems reasonable, as long as you remember to turn them back on if you need to go missed.”
The flight’s operator, Luxwing, had a fleet of 21 business jets, including 7 Phenom 100’s. Its flight operations department was supposed to check that the landing performance of its airplanes was adequate for the forecast conditions at the destination airports. Apparently, they did not do that for the Paris flight.
In February of 2013, a Phenom pilot lost control of the airplane in the flare while attempting to land at Berlin-Schönefeld airport in Germany. The German safety investigation agency, the BFU, found that the crew flew the approach in known icing conditions and did not activate the wing and horizontal stabilizer de-icing system. A build-up of ice on the wings and the horizontal stabilizer and the flight’s slow approach speed caused the airplane to stall.
The agency thought the crew did not understand the connection between the de-icing system and the stall warning system and recommended additional training for pilots receiving EMB-500 type rating training.
In December 2014, another Phenom 100 crashed while on approach to Gaithersburg airport (GAI) in Maryland. The three people on board and three other people on the ground were fatally injured. The NTSB said the probable cause of the accident was “the pilot carrying out an approach at a landing speed below that recommended in the manufacturer's normal procedures in icing conditions and the non-activation of the wing and horizontal stabilizer de-ice system. The combination of these two factors led to a stall at an altitude which made recovery impossible.”
The pilot was flying at the appropriate speed for non-icing conditions. He was probably very concerned about stopping on GAI’s 4,202 ft long runway 14. He had a previous runway excursion at that airport in another type of airplane and would have been very aware of the landing distances required. If he had attempted to land with the de-icing system on, even if he performed a flawless approach and touchdown, he would have only had about 100 ft. margin to be able to stop. With the de-icing system off, he had about a 1,700 ft stopping margin. In addition, with the de-icing system on, he did not have a sufficient rate of climb on one engine to conduct the approach.
As with the BFU, the NTSB recommended better training. They asked the National Business Aviation Association, manufacturers and training providers to develop better pilot training for winter weather. They also recommended that FAA and the General Aviation Manufacturers Association develop automatic icing alert systems.
A problem with the training recommendations is that the pilots in both the Berlin accident and the Gaithersburg accident probably knew that they were operating in violation of Embraer’s flight manual warning. Lack of adherence to a warning or standard operating procedure (SOP) is not a training issue, it’s a compliance issue.
The automatic icing alert system recommendation seems like a better idea. The NTSB’s recommendation was directed at turbofan airplanes that require a type rating, are certified for single-pilot operation and flight in icing conditions. The concern is that solo pilots flying turbine-powered airplanes in bad weather are so busy that they may not notice when the temperature and moisture require de-icing equipment to be turned on, and an icing light would be a helpful reminder.
Factors In Ice-Induced Hard Landings, Part 3
Roger Cox June 23, 2023
In February 2014, 10 months before the Gaithersburg crash, an Embraer EMB-145 regional airliner had a hard landing in icing conditions at Memphis, Tennessee. There were no injuries to the 44 passengers on board. While the first officer was applying control inputs to adjust for a crosswind, there was a rapid roll to the right, a wing strike and substantial damage to the airplane. The airplane was examined about 40 min. after parking at the gate, and there was an accretion of ice on the leading edge of both wings.
The airplane was equipped with two ice-detector units, with sensors located on both sides of the nose. The airplane’s ice-protection system uses either bleed air or electrical power and is fully automatic. When either of the ice detectors detect ice, an advisory message "ICE CONDITION" is shown on the EICAS display, and a signal is sent to the anti-icing system valves to activate them to open, and a signal is sent to the full authority digital engine control (FADEC) to activate the automated engine icing thrust setting. The ice detectors are self-monitored and activate a caution message when a detector fails.
The last ATIS broadcast before the accident reported tower visibility of 1/2 mile, ceiling overcast at 400 ft. agl, temperature 1C, and dew point temperature -1C. An NTSB aircraft performance study showed that the airplane was in icing conditions for at least 20 min. before the accident. However, the ice-detection system never activated.
The study concluded that the right roll happened due to ice buildup, but the airplane did not experience a full stall. There was enough ice to create flow separation on one wing in the flare but not enough to affect control of the aircraft during the approach.
The ice-detection and anti-icing systems were tested, both on the airplane and at the manufacturer’s facility, and no faults were found.
The company’s airplane operating manual and SOPs said the crew was responsible for monitoring icing conditions and manually operating the ice- protection system if necessary. However, the company’s flight standards manager said manual operation of the anti-icing/de-icing systems was not emphasized in training.
The NTSB could not determine why the automatic ice-detection and protection system did not work. They concluded that the crew failed to adequately monitor the system.
The Memphis accident proved that while an ice detector can be useful, it is easy to over-rely on the system and that there is no substitute for the crew to actively monitor ice conditions and the status of protection systems.
In the Paris case, the BEA did not provide a succinct probable cause statement, but provided a concluding discussion. They said the ice on the leading edge of 9H-FAM did not fully break off when the de-icing system was used, and it reformed. The stall warning system (SWPS) was not configured to alert the crew that they were flying close to stall speed. The pilots either didn’t see the ice buildup or ignored it.
They then said that the aircraft’s landing performance penalties in icing conditions frequently caused crews to make risky approaches. “Commercial pressures associated with this type of operation may encourage crews not to comply with the proper procedures for the approach and landing in icing conditions by deactivating the de-ice systems as soon as they visually observe that the leading edges of the wings are free of ice,” wrote the BEA. In addition, “The crews who have to fly in icing conditions are then faced with difficult choices: either refuse to carry out the flight, or accept a very high probability of diversion, or lastly accept a deviation from procedures and take the risk of landing with a contaminated aircraft.”
As with the NTSB, the BEA recommended ice detectors on all EMB-500 Phenom 100 aircraft. The Phenoms equipped with a Garmin G3000 avionics suite already have ice detectors, and Embraer issued a service bulletin in October 2019 that permitted installation of an ice detector on the other Phenom’s that have the older G1000 suite. As of November 2021, 39 out of 376 Phenom 100’s had ice detectors installed.
They also recommended that operators pay more attention to the performance limitations of the aircraft when choosing the type of aircraft for each mission, and that the European Union Aviation Safety Agency (EASA) revise certification criteria to include icing performance issues that are hard for crews to manage.
From my perspective, it appears that the Paris crew was put in the position of choosing between having to land without using their de-icing equipment or failing to deliver their passenger to his intended destination. Furthermore, this has been a common dilemma for crews.
Better training, ice detectors, and more conservative and safety-oriented flight planning should all help to prevent this type of accident. I would add the following simple rules:
- There is no substitute for disciplined adherence to flight operations manual limitations, procedures and warnings.
- It is always necessary to monitor ambient temperatures and moisture.
- It is dangerous to dispatch a flight to a destination with forecast icing conditions when you know the airplane cannot land with the de-icing equipment on.
Factors In Ice-Induced Hard Landings, Part 1: https://aviationweek.com/business-aviation/safety-ops-regulation/factor…
Factors In Ice-Induced Hard Landings, Part 2:
https://aviationweek.com/business-aviation/safety-ops-regulation/factor…
Roger Cox
A former military, corporate and airline pilot, Roger Cox was also a senior investigator at the NTSB. He writes about aviation safety issues.
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