Category: Flying

Has anyone ever seen an explanation of why Boeing couldn’t simply remove MCAS from the 737 MAX and tell pilots “you have to push forward on a go-around, just as you would in a Cessna 172 or Cirrus SR22”?

From FAR 25 (certification of airliners):

§25.145   Longitudinal control.

(a) It must be possible, at any point between the trim speed prescribed in §25.103(b)(6) and stall identification (as defined in §25.201(d)), to pitch the nose downward so that the acceleration to this selected trim speed is prompt with

(1) The airplane trimmed at the trim speed prescribed in §25.103(b)(6);

(2) The landing gear extended;

(3) The wing flaps (i) retracted and (ii) extended; and

(4) Power (i) off and (ii) at maximum continuous power on the engines.

(b) With the landing gear extended, no change in trim control, or exertion of more than 50 pounds control force (representative of the maximum short term force that can be applied readily by one hand) may be required for the following maneuvers:

(1) With power off, flaps retracted, and the airplane trimmed at 1.3 V_SR1, extend the flaps as rapidly as possible while maintaining the airspeed at approximately 30 percent above the reference stall speed existing at each instant throughout the maneuver.

(2) Repeat paragraph (b)(1) except initially extend the flaps and then retract them as rapidly as possible.

(3) Repeat paragraph (b)(2), except at the go-around power or thrust setting.

(4) With power off, flaps retracted, and the airplane trimmed at 1.3 V_SR1, rapidly set go-around power or thrust while maintaining the same airspeed.

(5) Repeat paragraph (b)(4) except with flaps extended.

(6) With power off, flaps extended, and the airplane trimmed at 1.3 V_SR1, obtain and maintain airspeeds between V_SW and either 1.6 V_SR1 or V_FE, whichever is lower.

In other words, an airliner meets certification standards unless it takes more than 50 pounds of push-forward on a go-around. I’m sure that there is some pitch-up moment on a 737 MAX, but it is tough to believe that a gradual trim-forward from MCAS would be sufficient if, in fact, more than 50 pounds of pushing on the yoke were required in the absence of any trimming.

The B737 already had a stick shaker for any time that it was getting near a stall (reminds pilots to push forward). So it should have been less likely to get into an elevator trim stall than a flight school Cessna 172.

Why couldn’t Boeing rip out MCAS, fire any of the coders and engineers involved in its design, tell airlines to give everyone an elevator trim stall demo in every recurrent sim session, and call the 737 MAX good?

(This is such an obvious and cheap fix that surely Boeing would have tried it if would work, so I assume that some rule would be violated, but which one?)

Related:

• https://philip.greenspun.com/blog/2019/04/08/boeing-737-max-crash-and-the-rejection-of-ridiculous-data/
• https://philip.greenspun.com/blog/2018/11/11/boeing-737-crash-is-first-mass-killing-by-software/ (how a conventional pusher system works)

Full post, including comments

Friends have been asking me about the Sikorsky S-76 helicopter crash that killed Kobe Bryant today. weather.com says that the crash occurred on January 26 close to 10:00 am and that conditions were cloudy/foggy.

Calabasas, California is between the Burbank and Camarillo airports. Here are their respective weather reports from around that time (10:00 am California time is 18Z). Burbank was right on the edge between visual and instrument flying conditions:

KBUR 261753Z 00000KT 2 1/2SM HZ OVC011 12/09 A3016

Translation: Burbank airport, 26th of the month, 17:53 UTC (9:53 am Pacific Standard Time), wind calm, 2.5 miles of visibility (“statute miles”), haze, temperature 12C, dewpoint 9C, altimeter 30.06. The nearly adjacent Van Nuys, airport, …

KVNY 261751Z 00000KT 2 1/2SM HZ OVC013 12/09 A3016

(almost identical)

Camarillo, closer to the coast, was slightly better:

KCMA 261755Z 03003KT 4SM HZ OVC017 15/11 A3019

26th at 1755Z (9:55 am), wind from 030 (NE) at 3 knots, 4 miles of visibility, haze, overcast clouds at 1,700′.

Over the hill at the Santa Monica airport that Californians are always getting into fights about?

KSMO 261751Z 12003KT 5SM HZ OVC018 14/09 A3018

(Translation: Santa Monica airport, Jan 26 at 17:51Z (9:51 am local time), wind from the southeast (120) at 3 knots, 5 miles of visibility in haze, clouds 1,800′ above the airport, temperature 14C, dewpoint 9C, altimeter setting 30.18.)

Assuming that it was bad weather that led to this accident, the engineering question is “Why couldn’t the $10 million helicopter fly itself away from obstacles, the way that a $400 DJI drone can?”

A Sikorsky is equipped with multiple computer-readable attitude sources so that the onboard processors know whether the machine is pitched or banked. It has multiple GPS position sensors so it knows where it is. It has at least one terrain database so it knows where the obstacles are. It has autopilot servos capable of maneuvering the aircraft. Why doesn’t it have the intelligence to say “You’re about to hit something, would you like me to take over and fly away from these obstacles and park on the ramp at the Van Nuys Airtel so that we can all relax?”

From flightaware.com:

The track log shows a rapid climb during the last minute of the flight, perhaps an attempt to climb away from terrain (ignore the “PM” after the time; FlightAware translated to Eastern time):

Skyvector chart for the area in question:

Note the red circle indicating a temporary flight restriction around the crash area. Also note the “5.2” above the red circle, indicating that one has to be 5,200′ above sea level in order to clear all of the obstacles in this part of the chart. (Google Earth shows that the highest terrain near the media-reported crash site of the 4200 block of Las Virgenes Rd. in Calabasas is around 1,100′)

An alternative presentation of transponder (ADS-B) data from flightradar24:

A YouTube video puts together the flight’s track with Air Traffic Control communications (presumably from liveatc.net). The pilot reported being at 1,400′ or 1,500′ above sea level. The Burbank and Van Nuys airports are 800′ above sea level. So this was 600-700′ above the ground (low for an airplane, but within the realm of normal for a helicopter) and thus, if the cloud layer had a flat bottom and the weather reports over 1,100’+ ceilings were accurate, the helicopter should not have been in a cloud.

The pilot had held an instrument rating since 2007, though it can be difficult to maintain instrument proficiency in helicopters, which are seldom flown IFR:

He also held a flight instructor certificate, which has to be renewed every two years. He was qualified to act as an instructor for instrument flying in helicopters:

Related:

• “New York helicopter crash: why not robot intelligence?”, which concludes “We expect so much of our phones and so little from our aircraft”

Full post, including comments

Welcome to the middle of the coldest month of the year! Here’s an interesting video about corrections to instrument procedures when it is extremely cold.

Full post, including comments

Nearly two years ago, I wrote about Scott Booth, a helicopter pilot who suffered injuries in a Grand Canyon accident.

He was recently able to post an update to a GoFundMe page (put together by fellow pilots at Papillon). Simply being alive at this point is an accomplishment and it sounds as though he is making pretty good progress.

Readers: Merry Christmas! (and I hope that none of you end up going through what Scott Booth has)

Related (previous years’ Christmas greetings):

• https://philip.greenspun.com/blog/2017/12/25/merry-christmas-to-the-sea-turtles/
• https://philip.greenspun.com/blog/2018/12/25/merry-christmas-again-to-the-sea-turtles/

Full post, including comments