Tuesday, March 19, 2019

Ethiopian ET302 similarities to Lion Air JT610

Reports from Ethiopian investigators have implicated the same Angle of Attack (AoA) sensor malfunction that was observed on Lion Air. Lion Air captain AoA sensor read about 22 degrees higher than the First Officer AoA sensor (a large bias error). Initial assessment of Lion Air AoA failure modes did not reveal any obvious electrical malfunction that could create the bias. The simplest explanation was that the AoA vane had been bent, causing a gross aerodynamic offset in the readings. If ET302 encountered the exact same offset, with the likelihood of it being bent exactly the same way not being conceivable, some other factor must be in play. For example, the ARINC 429 representation of AoA uses two's complement fraction binary notation (BNR). It is interesting to note that bit 26 represents 22.5 degrees which would be the bit "flipping" between the Captain and F/O AoA values (all other bits would match).  Is it possible that the ARINC 429 word is getting corrupted (software defect)?  If the ET302 offset was something like 20 or 24, this theory falls apart.


With this in mind, what are the issues left to restore 737 MAX airworthiness?

Friday, March 15, 2019

What have we learned this week?

The crash of Ethiopian ET302 brought a tragic beginning to what must be one of the worst weeks in aviation, ending with the grounding of the Boeing 737 MAX. What does Lion Air JT043 and JT610 teach us? Did we, as an industry do everything we should after JT610? Accusations of impropriety levied at Boeing and the FAA seemingly are always on the ready. Adding to the week was an update on Atlas 5Y3591 which at first seemed to be one thing, but with a slight wording change thankfully seems to be another altogether.

Thursday, March 14, 2019

Comparing Ethiopian ET302 to Lion Air JT043, JT610

Did Ethiopian ET302 succumb to the same situation as Lion Air JT610? The FDR and CVR data is being processed as I write this, with a public release in some form expected by Monday March 18. Aviation authorities have grounded the Boeing 737 Max before receiving a report from this recorder data. The only information to the public is from commercial ADS-B data brokers, notably Flightradar24.com, whose recording is incomplete. Aireon has shared space-based ADS-B data with several parties, but not to the public. Canada and the US make reference to the Aireon data as a factor in their assessment, with the claim that there were sufficient similarities to be concerned.

Tuesday, March 12, 2019

Atlas Air 5Y3591 Dove because of Nose-Down Elevator Command

The NTSB has revealed that Atlas Air 767 Freighter flight 5Y3591 dove based on nose-down elevator command. The nose was pushed over 49 degrees nose down. The engines were brought up to full thrust. There was no stall warning that preceding these actions. The dive reached 430 knots before impacting. Pitch attitude rose from -49 deg. to -20 deg. in the dive.

Saturday, March 9, 2019

Exploring Rain Fade in an Extreme Rain Fall Zone


Rain Fade is a factor with Ku-band and Ka-band satellite communications.  Rainfall rate is measured in mm/hour. The occurrence of significant Rain Fade events is scaled by the rainfall rate and its duration. Generally these events are transient as the rain cloud moves through. The path of interest is only the line from the satcom terminal to the servicing satellite. Only while the rain cloud is in the way do problems occur.

Panama is in a very severe rainfall rate region and will create frequent issues with Ka band service operating below about 15,000 feet. Ku should operate through these scenarios with less disruption. It is prominent in the region along with the Brazilian rain forests and significant as a hub airport. 

Friday, March 8, 2019

5Y3591 Stabilizer Trim Actuator appears to be Nose Down

When KHOU took a video tour of the collected wreckage, they included a frame of the stabilizer trim actuator (the jackscrew).

Thursday, March 7, 2019

Limiting RF exposure to Humans in Close Proximity to Satellite Transmitters

Satellite radios produce powerful Radio Frequency (RF) emissions. A method is provided for limiting the RF exposure to humans that are in close proximity to satellite transmitter antennas by establishing radial keep-out zones.

Wednesday, February 27, 2019

More Questions Raised for Atlas 5Y3591 Loss of Control

Atlas 767 flight 5Y3951 was descending for 3,000 feet when it appears to have briefly leveled off at 6,200 feet, before nosing over and plunging to the ground.

Sunday, February 24, 2019

NTSB Brief Atlas 5Y3591 Sun 4pm CST

NTSB chairman Sumwalt has seen video of the last five seconds to the impact of Atlas 5Y3591 and confirms it was in a steep, wings-level dive and made no visible attempt to pull up. The debris field is approximately 200 yards long by 100 yards wide in a NW orientation, consistent with the aircraft steep trajectory and high speed. The steep descent began with light to heavy rain in the area, from about 6,000 feet at 240 knots airspeed. There was no communication from the flight crew after their routine approach. They were descending from 18,000 feet for 3.000 feet when the event occurred. 

Saturday, February 23, 2019

Atlas Air 767 Flight 5Y3591 Plunges from 6,000 Feet


Three Atlas Air crew members tragically perished when their 26 year-old Boeing 767 plunged from about 6,000 feet in about 10 seconds. The freighter had departed from Miami and was on approach to Houston (IAH). The crew made no radio call, and there was no warning or indication of difficulty prior to the pitch over.

Friday, December 7, 2018

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.

Sunday, December 2, 2018

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

Friday, November 23, 2018

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.

Tuesday, November 20, 2018

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.

Thursday, November 15, 2018

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

Monday, November 12, 2018

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

Saturday, October 13, 2018

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.

Friday, October 12, 2018

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)

Friday, September 28, 2018

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.) 

Tuesday, September 25, 2018

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.

Thursday, September 20, 2018

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." 

Thursday, June 7, 2018

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.

Monday, April 30, 2018

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).


Monday, February 26, 2018

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.

Friday, February 9, 2018

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.

Sunday, January 28, 2018

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

Thursday, January 11, 2018

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.

Tuesday, January 2, 2018

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.

Wednesday, December 6, 2017

Project Paper 792 - Dec 2017 Update


Project Paper 792 System
Flat-Panel antennas, particularly those with embedded amplifiers, provide the only pathway from an effective 18" aperture from a typical multi-gimbal antenna to as much as a 42" aperture.   The first of these new antennas is the Gogo 2Ku made by ThinKom.

Project Paper 792 provides the form and fit of these second-generation satcom systems building on the baseline from ARINC 791 part 1 and using a common functional definition using ARINC 791 part 2 and Project Paper 848.

Friday, November 17, 2017

Comparing Antenna Performance

While it is possible to get 2x as marketing touts, the ThinKom (2Ku) antenna achieves about 1.5 times the spectral efficiency as a competing 2-axis antenna along typical routes. The ThinKom antenna may perform even better in the tropics, where the elevation angles may be highest.

The ThinKom antenna can operate without any performance reduction due to skew angles that may be encountered in the tropic regions, unlike a 2-axis antenna which may suffer severe degradation.

Theoretically, these same benefits await other flat-panel antennas.  Practically, no other antenna has  made public, legitimate claim to a design matching instantaneous bandwidth, efficiency, robustness, and scan loss, in the same size package.  VICTS weakness is cost, weight, form-factor; all of which electronic phased array may have advantage. 

Monday, November 13, 2017

Defense in Depth


Defense-in-Depth is a security concept that applies successive barriers to unauthorized access.  Aeronautical communication includes a Commercial-off-the-Shelf (COTS) layer, a Network layer, and an Application layer.

Friday, October 27, 2017

Space Shuttle Approach and Landing Test Program

Robert (Bob) Montgomery participated in the Space Shuttle Approach and Landing Test program, conducted by NASA Dryden at Edwards in 1977.  A Boeing Aerodynamicist, Bob conducted wind tunnel test to develop the control modifications as a result of carrying the Space Shuttle, and devised procedures so it could be safely separated.

Monday, October 23, 2017

Google Loon - Floating Nest of Radio Technologies

Google is deploying a High Altitude Platform System (HAPS) in the form of balloons that float around 20 km in altitude above a service area.  Representative link budgets for both the LTE service and the air-ground unlicensed feeder link show that one balloon can deliver about 10 Mbps uplink and 20-25 Mbps downlink, on average, to LTE subscribers in an 80 km coverage area.

Saturday, September 2, 2017

Managing Network Security and QoS: PP848

Air Transport Airplanes are faced with a monumental challenge to upgrade and embrace modern IP radio networks.  Network security has risen mightily to challenge designers, mire down operations, and yet struggles to achieve its goal.  Bandwidth management - Quality of Service - is done piece-meal, blind to real priority and performance goals.  What will bring this all together?

Friday, September 1, 2017

“Otto”, your new First Officer

Will air transport airplanes carrying many people for commercial purposes move to fully autonomous, no human pilot onboard? 

The First Officer will turn into “Otto”, a built-in feature of the next generation air transport airplane, and that the Captain is here to stay.   This is a logical progression from four to three (no Navigator) to two (no Flight Engineer) to one (no First Officer.)

Thursday, August 31, 2017

Antenna Performance along an Airline Route

Aircraft fly from a departure airport to a destination airport along a route that is ideally a great circle connecting the two airports.  Weather and other aircraft traffic, along with other considerations, can lead an airplane across a range of territory when flying the route from day to day.

Airplanes inherently favor flying wings-level while not maneuvering (as opposed to a slip.)  This leads to greatest passenger satisfaction and can avoid troubling issues with fluids.  As a result, the orientation of the airplane changes with respect to satellites operating along the geostationary orbit (GSO). The relative orientation between satellite and antenna leads to beam steering (azimuth, elevation, polarization skew) commands and also has an influence upon the airplane antenna performance.

Skew angle and Elevation angle from various satellite positions, flying Los Angeles to Sao Paulo, Multi-gimbal antenna

Wednesday, August 30, 2017

Choosing an Airline Wireless Internet Service Provider (WISP)

Airlines have been providing passengers radio communication services at their seat since 1937. 

In 2017, airline passengers yearn for free and compelling Wi-Fi Internet access. What should an airline consider when choosing an inflight Wireless Internet Service Provider (WISP)?

Monday, April 17, 2017

Spectral Efficiency - The Fitness of Wireless Communication

Spectral efficiency –the effective data rate that can be achieved from a given slice of spectrum. 

Saturday, April 8, 2017

Designing B-47 Maneuvers

The B-47 was the first swept-wing bomber. Boeing aerodynamicist Robert (Bob) Montgomery stopped by Pease AFB and briefed emerging maneuvers possible with the B-47.

Friday, March 17, 2017

Tom Kraft - Final Clearance

Tom Kraft and Dave Allen share a beer moments after FANS was first certificated by the FAA (1995). 
Not pictured were Tom Twiggs (Boeing project pilot) and 
David Massey-Greene (QANTAS Chief Technical Pilot) on the other end of the table.
Sadly all four are gone
Tom Kraft died yesterday in an accident, at his home looking out on Hood Canal. His tragic passing comes less than a year after retiring from a 30+year career at the FAA, leading air traffic control into the digital age.

Saturday, March 11, 2017

Project Paper 848 Draft 1 Released - Secure Broadband IP Air/Ground Interface (SBAGI)



Draft 1 of ARINC Project Paper 848: Secure Broadband IP Air-Ground Interface (SBAGI) has been released by the AEEC Network Infrastructure and Security (NIS) Subcommittee for industry comments.

Monday, January 23, 2017

TK295, URSS Sochi Runway 02, Sep 27 2016 TC-JLP A319 ATC Intervention in Go-Around

There is a difference in the reported actions (turn left) and the flightradar24.com data (turn right) after commencing a particular missed approach at Sochi in Sep, 2016.  The FR24 data offers a climbing right turn, whereas avherald depicts a left turn direct.  

Friday, January 20, 2017

Monday, January 16, 2017

TK6491 747-400F MyCargo/ACT Airlines, Manas Airport (FRU/UCFM) in Bishkek

Did a false glide slope lead TK6491 astray?  Never have heard of this before.
A 747-400F cargo plane with 4 crew crashed near Manas Airport, in a residential area just past runway 26 at about 07:18 local time (2017 01 16 0117Z).  All aboard and 35 on the ground perished.

Wednesday, January 4, 2017

SU1008 UMKK/KGD Kalingrad A321 VP-BES Runway 24 Departure

An Aeroflot A321departed runway 24 at UMKK Kanlingrad on Jan 03 2017 20:54.

Weather reports include forecast medium braking in wet snow, poor visibility, low ceilings with thunderstorms in the area, and a heavy crosswind.  The airplane ended up on the right side of the runway, about 5,500 feet from the runway threshold.  The crosswind was from the right, so the airplane deviated into the crosswind.

Runway 24 is 8202 feet long at 31 feet MSL.

flightradar24,com ADS-B data for SU1008

Thursday, December 8, 2016

Communications Assistance for Law Enforcement Act (CALEA)

https://www.documentcloud.org/documents/3229456-Thieving-Magpie-Using-on-board-GSM-GPRS-services.html

Sunday, December 4, 2016

LMI2933 LAMIA AVRO RJ85 Medellín Deadstick

LMI2933 approach to SKRG.  The airplane position is plotted as a function of time (where it effectively flows to the left). The airplane initially arrived with conceivably enough fuel to complete the approach and landing safely.  The airplane entered a holding pattern and on the back side of the second circuit departed the holding pattern with apparently total engine failure.

Wednesday, November 9, 2016

Galloping Gertie

The Tacoma Narrows Bridge opened to fanfare in July, 1940 having been constructed over the previous two years as a Public Works Administration Project.  The bridge donned the name "galloping gertie" during construction, giving to its narrow profile and insufficient stiffness. The bridge famously collapsed on Nov. 7, 1940.

“Pence Plane” EA3452 Overrun



Wednesday, October 12, 2016

FCC 15.247 (c) 2 Smart Antenna Systems - Powering Line-of-Site Aeronautical Communications

The FCC issued Report and Order 04-165 on July 12, 2004.  The Smart Antenna System (SAS), capable of forming multiple antenna beams, forged a pathway to frequency reuse and ultimately powers the unlicensed air-to-ground networks being developed by SmartSky Networks and Gogo.  A review of the FCC 15-247 offers an understanding of an overall system architecture and performance estimates.

Wednesday, September 28, 2016

Using Unlicensed Spectrum for Air-to-Ground Networks



Gogo has announced an initiative to utilize unlicensed spectrum to power an new Air-to-Ground (ATG) network.  They profess a beam-forming network deployed to their 200 plus ground stations will deliver 100 Mbps.  I believe that it is possible both Gogo and SmartSky are pursuing a similar technology.  The following is my analysis on SmartSky, to which it may relate to Gogo ATG as well.

Monday, September 26, 2016

Bluetooth Low Energy - Guiding our Way in the Future


Bluetooth Low Energy (BLE) refers to a low power broadcast mode commonly referred to as a beacon (Bluetooth beacon, iBeacon).  BLE broadcast is a limited protocol intended to be received only by proximate user devices (less than 100 meters).  The beacon presents "effectively" a unique serial number.  An application can lookup the location of a beacon by its serial number.  An application can use the BLE beacon-derived position to trigger appropriate actions.