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Wake Turbulence

Wake Turbulence

The European Aviation Safety Agency has published safety information bulletin SIB 2017-10 to remind pilots and air traffic controllers about the risks associated with wake turbulence encounters at high altitude and applicable precautionary measures. “With the increase in overall volume of air traffic and enhanced navigation precision, wake turbulence encounters in the en route phase of flight have progressively become more frequent in the last few years,” the bulletin said.

The document comes just six months after a Bombardier Challenger 604 at FL340 was severely damaged and its occupants injured when it encountered wake turbulence 12 nm from an Airbus 380 that had passed overhead in the opposite direction at FL350. As the bulletin noted, the so-called “heavy” and “super heavy” aircraft—such as the Airbus 340 and 380 and Boeing 747—are more prone to generate stronger vortices, although there is also potential from other large aircraft types.

Considering the high operating airspeeds in cruise and the standard 1,000-foot vertical separation in RVSM airspace, EASA said that wake can be encountered up to 25 nm behind the generating airplane, but “the most significant encounters are reported within a distance of 15 nm.” The bulletin concludes with illustrations that show various scenarios of wake turbulence encounters and recommended avoidance techniques.

See https://ad.easa.europa.eu/ad/2017-10

BREXIT: The impacts on the aviation regulatory regime

BREXIT: The impacts on the aviation regulatory regime

Until we know what is to happen next, here are some interesting titbits:

Pitot Tube problems receiving ongoing scrutiny

Pitot Tube problems receiving ongoing scrutiny

Pitot probe vulnerability is again receiving scrutiny from regulators following detailed reports on two inflight emergencies traced back to the systems.

The first, involving a United Airlines Boeing 757 descending into Dublin in October 2013, was chronicled in a recent issue of this magazine (AW&ST May 23, p. 32). The report by Irish investigators cited two probable causes: A temporary blockage of the right main pitot tube due to icing, leading to an inaccurate low-airspeed indication on the first officer’s display and the crew’s non-standard response to the low-airspeed reading. The Irish Air Accident Investigation Unit’s report included eight recommendations, including for the FAA to “study whether a safety deficiency exists in pitot probe icing protection” for aircraft certified before January 2015, when enhanced certification standards went into effect. Those changes were triggered in part by the investigation into the June 2009 Air France Flight 447 accident, which determined that inconsistent airspeed readings between the captain’s and first officer’s displays started the chain of events that led to an aerodynamic stall.

A month after the United incident, industrious mud-dauber wasps took less than 3 hr. to build a nest in the pilot’s-side pitot probe of an Etihad Airways Airbus A330 on the ground at Brisbane Airport in Australia, triggering a series of troubling events, an Australian investigation found. The undetected blockage of mud resulted in an aborted takeoff that was followed by an inconclusive troubleshooting effort by maintenance technicians and a second takeoff for Singapore. That departure was quickly followed by a Mayday call by the pilots, who promptly returned to Brisbane. Several organizations affected by the incident instituted changes based on the investigation, an Australian Transport Safety Bureau’s (ATSB) report explained. The airport instituted multiple operational changes, Airbus modified its maintenance troubleshooting manual, and Etihad began requiring ground crews to install pitot probe covers at Brisbane “irrespective of ground time.”

Investigators determined that the nest blocked the captain’s pitot tube, resulting in a red “speed flag” display on the avionics as the aircraft accelerated through 50 kt. on the first takeoff attempt. Per standard operating procedures (SOP), the captain rejected the takeoff. The A330 has three open-face pitot tubes-a captain’s probe, first officer’s probe and standby probe-on the underside of the fuselage near the nose, devices that measure ram air pressure that is converted to airspeed readings by the avionics.

Maintenance technicians relied on two procedures in the A330 troubleshooting manual (TSM), neither of which identified the pitot probe as a possible root cause for the airspeed indication problem. The ATSB noted that Airbus had sent out a service letter to operators prior to the incident, linking airspeed discrepancies to potential pitot probe problems. The airframer in October 2014 updated the TSM to include the additional information.

The A330 was cleared for departure after a few minor avionics configuration changes, but the captain’s airspeed indicator again failed during the takeoff run, this time at a speed where SOPs called for continuing the takeoff. The ATSB questioned the captain’s recollection that the airspeed failed after “V1” (151 kt.), the speed at which crews are advised to continue the takeoff, noting that the flight data recorder information showed that the failure flag should have appeared after reaching 50 kt.

Once airborne, the sensor issues caused the A330’s fly-by-wire flight control logic to revert to alternate law and various slat and flap warnings occurred. The pilots declared an emergency and landed at Brisbane at an aircraft weight of approximately 200 metric tons, 18 heavier than the A330s 182-metric-ton maximum landing weight.

http://aviationweek.com/mro/pitot-tube-problems-receiving-ongoing-scrutiny?NL=AW-05&Issue=AW-05_20160622_AW-05_554&sfvc4enews=42&cl=article_4&utm_rid=CPEN1000001748382&utm_campaign=6275&utm_medium=email&elq2=e4519e892c8846979adb383d3876ebc8

UAV: New system helps aircraft automatically avoid mid-air collisions

UAV: New system helps aircraft automatically avoid mid-air collisions

A research effort associated with DARPA’s Aircrew Labor In-Cockpit Automation System (ALIAS) program recently conducted the first successful flight tests of a shoebox-sized, plug-and-play system designed to enable manned and unmanned aircraft to automatically detect and avoid potential mid-air collisions. An unmanned air vehicle (UAV) repeatedly used the technology demonstration system to detect and track in real time a Cessna 172G aircraft approaching from various vertical and horizontal distances.

See image here http://www.darpa.mil/ddm_gallery/Sense-and-Avoid.png

See video here. https://www.youtube.com/watch?v=ZN2ZiyVffPI

An unmanned air vehicle (UAV) repeatedly used the technology demonstration system to detect and track in real time a Cessna 172G aircraft approaching from various vertical and horizontal distances.

The integrated sense-and-avoid (SAA) system includes a single optical camera that provides imagery for detection and tracking. The system also incorporates passive ranging features that assess the likelihood of an incoming aircraft intersecting the flight path of its host aircraft, and collision-avoidance capabilities to determine the best way to steer the host aircraft out of harm’s way.

The work is part of a DARPA effort to create a low-cost, easily installed system to detect oncoming or crossing aircraft and determine the best avoidance strategy compliant with standard rules that set minimum vertical and lateral distances between aircraft during flight.

“This successful flight test is a step toward adding external perception to ALIAS’ toolkit for advancing in-flight automation,” Dan Patt, “What pilot wouldn’t want to set a box on their dashboard that would provide an additional pair of eyes to alert of potential collisions? This SAA system has the potential to enable a wide range of manned and unmanned systems to safely integrate into an increasingly populated and complex airspace.”

DARPA has been developing this capability over the past two years and put the technology demonstration system through extensive preliminary testing before the recent flight tests, which evaluated only detection and tracking. Based on the success of those flights, DARPA is planning another phase of the effort, which includes joint funding from the U.S. Air Force Research Laboratory (AFRL).

This follow-on research would shrink the system size; further test the ranging and collision-avoidance features; mature additional capabilities of the system such as detecting aircraft below the horizon and in poor light conditions; and improve calculations for optimal aircraft trajectories to avert impending collision.

The system could ultimately serve as a line of defense in future layered air-traffic management systems that could include Automatic Dependent Surveillance-Broadcast (ADS-B) transponders and ground-based radar systems that are part of the federal NextGen effort. There is particular potential applicability for unmanned air systems or aircraft with reduced crew sizes.

The ALIAS program envisions a tailorable, drop-in, removable kit that would enable high levels of automation in existing aircraft and facilitate reduced need for onboard crew.

The program intends to leverage the considerable advances that have been made in aircraft automation systems over the past 50 years, as well as the advances that have been made in remotely piloted aircraft technologies, to help shift and refocus pilot workloads, augment mission performance and improve aircraft safety.

http://www.spacedaily.com

Boeing, FAA warn 787 pilots of bad airspeed data

Boeing, FAA warn 787 pilots of bad airspeed data

Boeing 787 pilots are being warned not to make sudden control inputs in response to a “sudden, unrealistic” drop in airspeed shown on cockpit displays.

The US Federal Aviation Administration (FAA) will adopt an airworthiness directive on 1 April requiring 787-8 and 787-9 operators to update the flight manual with the warning message.

The FAA accelerated the release of the airworthiness directive, bypassing the normal rulemaking process to make operators adopt the change as quickly as possible.

Boeing made an identical recommendation to 787 operators on 4 March, which the FAA directive will make mandatory.

The fleet has made three reports of displayed airspeed plunging significantly below actual airspeed, the FAA says. In each case, the 787 was flying in conditions involving significant water ingestion and possibly icing of two of the three pitot tubes feeding speed and altitude information to the air data system.

The FAA and Boeing are continuing to investigate the cause of the erroneous displayed speed changes.

In one case, the pilot reacted to the inaccurate data by commanding a “significant” nose-down dive, over-riding the auto-pilot in the process.

Boeing and the FAA are concerned that a pilot might command a dive that exceeds the structural limits of the 787, as a response to erroneous information from the air data system.

While the cause of the erroneous data is being investigated, 787 operators must update the manual to instruct pilots to not apply “large, abrupt control column inputs” in response to an “unrealistic” drop in displayed airspeed.

https://www.flightglobal.com/news/articles/boeing-faa-warn-787-pilots-of-bad-airspeed-data-423735/

See also http://www.wsj.com/articles/faa-issues-safety-directive-concerning-airspeed-sensors-on-boeing-787-jetliners-1459467143