Phenom 100 blowouts prompt FAA scrutiny
For the third time this year, an Embraer Phenom 100 suffered a dual tire blowout upon landing after a reported failure in the brake-by-wire system. The most recent incident occurred on September 25 in Arizona as the light twinjet landed at Phoenix-Mesa Gateway Airport. According to an airport official, the Phenom had just taken off and retracted its gear when the pilot noted a brake failure warning on the aircraft’s engine indication and crew alerting system (Eicas) and immediately notified the tower of his intention to return.
Upon landing, the pilot said he “had no brakes and used the ‘parking brake’ to slow the aircraft.” After both main tires blew, the aircraft spun on the runway but did not exit it. The Embraer-owned service center located at the airport replaced the tires and the Phenom was towed from the runway.
This follows incidents on September 10 in Brenham, Texas, where a Phenom 100 departed the runway after it suffered a dual blowout, and one on March 4 in Mammoth Lakes, Calif. In both of those mishaps, the aircraft displayed a brake failure caution message before landing and required the use of emergency brakes to stop. No injuries were reported in any of the incidents.
The FAA issued a statement noting it is aware of Phenom 100 brake issues and is addressing them with its Brazilian counterpart and the airframer. “Embraer has issued service materials for two identified issues, and there is ongoing evaluation of the root causes for at least two additional components that might be contributing,” the U.S. agency stated.
Brake System Improvements
In May, the Brazilian manufacturer issued an operational bulletin regarding appropriate brake cool-down times and brake checks after any landing, rejected takeoff or extended taxiing, stating it has noticed that “under certain conditions, the brake assembly temperatures might reach levels that could lead to a malfunction of a shuttle valve assembled to it. Possible consequences are temporary loss of main brakes during taxi, followed or not by BRK Fail CAS message.”
That bulletin was followed a day later by a service bulletin (revised most recently in August) that dealt with the replacement and installation of a new shuttle valve in the Meggitt brake system, which was expected to improve the system’s “margins with respect to temperature, avoiding the possibility of malfunction.” The service bulletin covered more than 150 aircraft in the fleet, which has thus far flown more than 30,000 hours.
According to Edson Mallaco, Embraer’s vice president for customer support and services, executive jets, approximately 70 percent of the affected aircraft have already incorporated the service bulletin, but, citing the ongoing investigation, he declined to state whether either of the aircraft involved in the September incidents had previously undergone the modification.
In its response to the incidents, Embraer said it “is aware of recent landing events associated with actual or suspected loss of normal brake system in the operation of certain Phenom 100s,” but noted that it could not comment further due to the ongoing NTSB investigation, to which it says it is contributing its full support. The company cautioned that the “reported brake events may have been caused by a different number of factors and it is premature to establish any connection between the relevant scenarios at this point.”
Mallaco told AIN that Embraer is aware of at least one instance where a tire blowout on the Phenom was caused largely by operator factors, when the pilot overshot the runway landing area and had to stop in a reduced distance. He also stated that any potential problems with the brakes would not apply to the 100’s larger stablemate, the Phenom 300, as the brake systems in the two aircraft were designed by separate companies.
Tom Latson (firstname.lastname@example.org), the NTSB’s investigator-in-charge of the incident at Brenham, Texas, told AIN that he would like to hear from any Phenom 100 operator who has experienced a BRK Fail Eicas warning in the past. Among those would be Jim and Betsy Frost, owners of the first Phenom 100, who took delivery of their aircraft less than two years ago. Since then, they have experienced three brake failure incidents, although none resulted in a tire blowout. Their first experience was a brake fail warning upon landing, the result of a failure of the right brake control valve. In this instance, Betsy Frost was able to stop the aircraft using only the left brake.
The next incident occurred during a long-distance taxi at Las Vegas McCarran International Airport. The main brake system failed and the aircraft was stopped with the emergency brake. According to Jim Frost, the investigation of this situation prompted a redesign of the shuttle valve in the brake system, which was overheating and sticking in an incorrect position.
Their last incident was similar to the most recent occurrences. Upon departing from a small Texas airport, the couple received a brake fail warning, which eventually cleared itself. As they landed at Houston Hobby Airport, the Frosts planned to divert the 20 miles to George Bush Intercontinental Airport with its 12,000-foot runway, if the brakes failed. Although the airplane stopped without difficulty, Embraer replaced both brake control valves and the brake control unit, and took the old components for examination.
While he has not experienced a blowout, Jim Frost (who also heads the Phenom Pilot/Owners Association) believes that in those recent instances where the pilots received brake failure notification soon after takeoff, they would have had ample opportunity to avoid damage to the aircraft by selecting an alternate airport with a long, wide runway. “Given an eight- or ten-thousand-foot runway, stopping the Phenom with the emergency brake system should not be too difficult, but trying to land on a six-thousand foot runway can be very difficult,” he said.
“The emergency brake system requires a good deal of force to pull and has quite a bit of travel before it engages. Once it engages, the displacement between light brake pressure and wheel lock is relatively short, so the pilot has to have the time and runway length to stop the aircraft without blowing the tires.”
Embraer’s Emergency Brake Procedure
In response to three dual-tire blowouts this year, Embraer is evaluating whether additional clarifications to its flight operations manuals could enhance the pilot’s preparedness when application of the emergency brake might be required. In an e-mail sent last month to Phenom 100 owners and operators, the airframer highlighted several procedural aspects for pilots regarding the use of the aircraft’s emergency brakes:
• Multiply the full-flaps unfactored landing distance by 1.5, according to what is currently stated in the AFM and QRH procedures.
• Start to apply the emergency brakes only after touching down the nose landing gear and controlling the aircraft.
• Pull the emergency brakes handle progressively until the emergency brake light turns on, and maintain this level of application.
• Pull the handle beyond this point only if required, after evaluating the runway conditions and the amount of landing field length remaining.
• There is no anti-skid function in the emergency brake system, so caution shall be taken during emergency brake actuation to avoid tire skid and consequently tire blowout.