Stopping Distance

Runway factors change the normal stopping distance of a Boeing 737-700. 

• A 10 knot tailwind adds about 21% to the stopping distance
• A wet runway adds about 15% to the stopping distance
• Standing water can more than double stopping distance.

Southwest WN278 overran the KBUR (Bob Hope, Burbank, BUR) runway 08. The Boeing 737-700 rolled into the Engineered Material Arrest System (EMAS) that had been installed as a result of another Southwest 737-300 which overran the same runway in March 2000. This was the second airplane to be fortunate for arrestment by that particular EMAS installation.

Lateral approach path shows a correction right-to-left on short final, which may have led to running off the left side of the runway. The last recorded speed of 49 knots at the runway end, after a normal arrival point, and expected touchdown point (assuming appropriate landing weight), leaves standing water/hydroplaning as the most likely overrun villain. There is no data to confirm the reason for lack of deceleration and control; only data to show it did not (which is evident in its final resting position). The nose-gear entered the EMAS probably traveling between 35 and 40 knots.

Aviation safety initiatives demand improvements to limit recurrence of the same factors that cause an accident or injury. While two Southwest 737s have overrun the same runway, this time EMAS brought the Southwest airliner to a rapid stop without significant injury.

Angle of Attack Vane Failure Modes

Lion Air JT610 Captain's angle of attack (AoA) measurement was about 20 degrees higher that the First Officer's AoA. The excessively high AoA value caused considerable flight deck effects, which may have been a principal factor in the catastrophe. Electrical and mechanical malfunction characteristics of the AoA transmitter are matched against observations. The most likely failure is mechanical in nature, influenced by air pressure, and fully internal to the AoA transmitter.

UTC Aerospace Systems (Rosemount) Model 0861 AoA Transmitter

First Look at JT610 Flight Data

Partial release of flight data from JT610 (h/t to Don Thompson). In short summary, the left Angle of Attack (AoA) vane was substantially offset from the right vane from taxi out. The left stick shaker activated on liftoff and stayed on for most of the accident flight. MCAS trimmed nose down when flaps were up. In a deadly game of tag, the Pilot stopped MCAS by manual trim nose up, but MCAS would start again five seconds later.  In each excursion, the stabilizer was held roughly in trim. There are 26 occurrences of MCAS trim down, pilot trim up.

It may have been the point when the captain transferred control to the first officer that MCAS was successful in two successive cycles, trimming the stabilizer nose down over four units without opposition.

The captain seems to have taken control back in the end, and pulls the column hard aft. MCAS is able to trim yet another one unit nose down before the captain stops it, but there is no subsequent  significant command to trim stabilizer nose up. The airplane dive exceeded 450 knots by the point of impact.

The prior flight showed similar behavior. But on that flight, the flight crew appear to have quickly cutout the electric trim altogether, and completed the flight trimming the stabilizer with the wheel.

Search for the CVR continues.

737 FCC Pitch Axis Augmentation - Command Integrity Mandate for Dual Channel, Fail-Safe

A line is drawn between primary flight controls that the pilot handles directly through control column, rudder pedal, and stabilizer trim; and automatic control, such as the autopilot, which manages the same surfaces through computer command. 

The Yaw Damper is an example of an automatic flight control system added to the airplane to augment flight characteristics. The Yaw Damper operates regardless whether pilot manual flight control or automatic flight control.

FCC Pitch Axis augmentation (Mach Trim, Speed Trim, and MCAS) commands may be based on a single sensor input. These commands should be checked against a calculation based on a second sensor set before becoming valid. A software update to the FCC may provide support for a dual channel mandate.

737 MCAS - Failure is an Option

The 737MAX introduced a new feature, Maneuvering Characteristics Augmentation System (MCAS). MCAS commands the stabilizer to trim down (only while flaps are up) in steps.  From reports, the aft column cutout switch is disabled while MCAS is active.  MCAS commands nose down trim at 0.27 deg/sec for about 10 seconds at a time. It then pauses briefly (duration not known, but presumed five seconds).  The time history of a fabricated scenario, starting at a stabilizer position of 8 units, shows it would take about 55 seconds to reach the nose-down limit. Starting at a more nose down position takes less time, e.g from 4 degrees about 35 seconds).

MCAS Commanded Stabilizer Trim Without Stopping

Stabilizer Trim

LionAir JT610 plunged into the sea from what may have been the result of runaway stabilizer trim.  The details are not released, but the FAA has issued an Airworthiness Directive drawing attention to the recovery from such an event.  What is stabilizer trim and why would it runaway?

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/83ec7f95f3e5bfbd8625833e0070a070/$FILE/2018-23-51_Emergency.pdf

Coverage Along a Route - Europe

Airlines flying routes connecting European airports fly far enough north to limit satellite elevation to less than 45 degrees. Installing a Ku/Ka band satellite antenna in the Airbus-nominated position for A320 series creates a blockage from the tail (shadowing) that can extend more than 30 degrees in elevation and about 4 degrees wide. This combination can lead to loss of service when the airplane is flying directly away from the servicing satellite. The problem is made worse by using satellites that are not well situated.

Close Calls Coming (TG679) and Going (IX611)

ADS-B OUT data broadcast coupled with machine learning can create a great enhancement to aviation safety. Flight Operations Quality Assurance (FOQA) was conceived as an anonymous means to reveal unsafe trends. The post-flight evidence would guide training and awareness, not personal vendetta. With ADS-B, the alerting can be done in real-time; the trends recognized as they are occurring.

IX611 Takeoff normal (A) and accident (X)

Using True Time Delay to Increase Instantaneous Bandwidth in a Phased Array Antenna

The progression towards High Throughput Satellites is enabled by frequency reuse using larger and larger bandwidth signals.  Bandwidths exceeding 100 Mhz are commonplace, with 250 MHz and larger bandwidths evident. A phased-array antenna belies the concept of using phase control to form a beam (or inherently, steer the beam electronically.) 

APEX 2018 Midway Report

APEX EXPO 2018 got started a day earlier than I expected.  My report from the first two days looking at VR headsets, satcom partnerships and agreements, seeking profit, and emerging technology.

Panasonic adds Inmarsat GX to the Routing Table

Panasonic and Inmarsat have jointly announced an agreement to work together.

• Panasonic will offer Inmarsat as their exclusive Ka-band satcom supplier
• Panasonic will continue to operate and grow their Ku-band network 
• Inmarsat will be able to bundle in Panasonic IFE and support as a part of their offerings
• Panasonic and Inmarsat will jointly develop a new Inmarsat GX terminal

"Customer airlines will be able to select a product that represents the best that Inmarsat and the best that Panasonic offer together" declared Ian Dawkins, Panasonic Senior VP of Network Operations. "This is far more than a simple reseller agreement." 

Aviation Cybersecurity 101

Thanks to Woodrow Bellamy III and Mark Holmes for inviting me to present at the Global Connected Aircraft Summit 2018.

Here is my slide deck (with notes). I have revised and added a slide to address how an iPad can host type B EFB messages.

Lion Air PK-LOO JT-892 Departed runway after touchdown

Joining final approach very late may have contributed to a Boeing 737-800 departing the runway 27 at GTO/WAMG Gorontalo Jalaluddin Airport in Indonesia at about 18:35:30L (10:35:30Z).

Seamless Air Alliance - Who Owns the Customer?

Delta, Airbus, OneWeb, Sprint, Airtel, and Gogo announced the formation of the Seamless Air Alliance.  

Equipment, certification, satellite coverage, billing and overall service is included as a one-stop offering.

A participating airline picks parts from a catalog, installs per a cookie-cutter, turns it on, and the passengers connect to the Internet.

Malfunction in an Aero Ku/Ka-band Satcom System

Ku/Ka-band Satcom Systems offer no safety functions. 

No failure of the satcom system should create an unsafe effect.

Users of the satcom system do so at their own peril, as they would with any Internet access provider.

Discovery of cybersecurity vulnerabilities should emphasize rapid response to close the threat and a cooperative approach to sharing information privately, with an agreement to share enough information publicly to raise awareness of best practices.

Details and a checklist in the following paper.

PP792 Mark 2 Satcom Advanced Features

PP792 defines the form and fit characteristics of the Mark II Aviation Ku-band and Ka-band Satellite Communication (satcom) System, intended for installation in all types of commercial air transport aircraft. The satcom system described in PP792 represents the next evolution from the Mark I system defined in ARINC Characteristic 791, Part 1.

Significant advancements include:

• Single, standard installation, no customization, fully interchangeable
• Smaller: no KRFU, Virtual APM
• Lighter: smaller connectors, fewer wires, no hyper-critical wiring, coax, or waveguide
• Flexible lug pattern accommodates two apertures, each up to 42"
• High power supply (2000 Watts) for large, solid-state, phased-array antennas
• Integrated Position, Attitude and Heading sensor
• High performance IF interface supporting NGSO networks

Is there Gold on Virgin America?

It’s like walking into a night club.

10 Years Later - Still Standardizing Aero Ku/Ka Satcom

With a two hour telecon in Jan 2008, the SAE/ITC AEEC Ku/Ka-band Satcom Subcommittee started to work together.  What ever happened?

10 years and 122 gatherings later, we are still at it!  Here we are today @ThinKom_Inc.

Regulating Radiated Emissions

https://transition.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet56/oet56e4.pdf

Equipment installed on aircraft must be designed and tested to be compatible with other equipment and with the airborne environment.  Notably, radio frequency (RF) radiated emissions from one system may disrupt other aircraft systems such as radio receivers or present hazards to human health.