Near miss at KMSP

[gismo]

Last night and this morning the news media has been busy reporting on a real near collision between an Airbus 320 passenger flight and a Beech 99 cargo flight. The Airbus departed 30R about the same time as the Beech took off from 30L (as cleared by the tower). As usual the reports are sketchy and confusing but it sounds like the tower expected the Beech to turn sooner than it actually did and based on that expectation had turned the Airbus into the path of the Beech. Somewhere it was stated that the Airbus got and responded to a TCAS alert (the reports indicate the Beech wasn't TCAS equipped although I was under the impression this was required for that size airplane) and it sounds like the Airbus passed over the Beech with about 100 ft of separation or less.

http://tinyurl.com/29rkenv

http://kstp.com/news/stories/S1758789.shtml?cat=1

http://www.startribune.com/local/minneapolis/103632674.html

 

[ScottM]

YIKES!

This sure sounds like something that was completely avoidable. A couple of questions.

The tower controller called the left turn of the AirBus? If so what responsibility does the tower have to ensure no loss of separation? I ask because I have heard time and again on this and other boards that the tower is only responsible for ensuring separation on the ground.

 

[jsstevens]

YIKES!

This sure sounds like something that was completely avoidable. A couple of questions.

The tower controller called the left turn of the AirBus? If so what responsibility does the tower have to ensure no loss of separation? I ask because I have heard time and again on this and other boards that the tower is only responsible for ensuring separation on the ground.

My understanding (weasel room here) is that depends on the class of airspace. In Class B ATC is repsonsible for separation of traffic in the airspace - that's why you can fly VFR in Class B only remaining "clear of clouds". In Class C and D it's only separation on the runway - and consequently the rules for cloud clearance are no different than normal VFR.

John

 

[TangoWhiskey]

My understanding (weasel room here) is that depends on the class of airspace. In Class B ATC is repsonsible for separation of traffic in the airspace - that's why you can fly VFR in Class B only remaining "clear of clouds".

John

True, but I'm not sure if the TOWER in class B airspace is responsible for separation in the air from the time traffic leaves the ground til they are handed off to departure. Departure/Arrival controllers in Class B certainly have responsibility for separation of all participating traffic. I know we have some controllers on this board and am interested to hear what they have to say.

In the transcript / audio on the 2nd link in the OP's story, the pilot was talking to MSP Departure; he'd already been handed off.

 

[Dave Siciliano]

Sounds like they were IFR and in the soup.

Dave


************************************************************
NTSB ADVISORY
************************************************************

National Transportation Safety Board
Washington, DC 20594

September 23, 2010

************************************************************

NTSB INVESTIGATING NEAR MIDAIR COLLISION OVER MINNEAPOLIS
INVOLVING COMMERCIAL JETLINER AND SMALL CARGO AIRCRAFT

************************************************************

The National Transportation Safety Board is investigating a
near midair collision between a commercial jetliner and a
small cargo aircraft that came within an estimated 50 to 100
feet of colliding near the Minneapolis-St. Paul Airport
(MSP).

On September 16, 2010, about 6:49 a.m. CDT, US Airways
flight 1848 (AWE 1848), an Airbus 320, was cleared for
takeoff on runway 30R en route to Philadelphia,
Pennsylvania, carrying five crewmembers and 90 passengers.
At the same time, Bemidji Aviation Services flight 46
(BMJ46), a Beech 99 cargo flight with only the pilot aboard,
was cleared for takeoff on runway 30L en route to La Crosse,
Wisconsin. Weather conditions at the time were reported as a
900-foot ceiling and 10 miles visibility below the clouds.

Immediately after departure, the tower instructed the US
Airways crew to turn left and head west, causing the flight
to cross paths with the cargo aircraft approximately one-
half mile past the end of runway 30L. Neither pilot saw the
other aircraft because they were in the clouds, although the
captain of the US Airways flight reported hearing the Beech
99 pass nearby. Estimates based on recorded radar data
indicate that the two aircraft had 50 to 100 feet of
vertical separation as they passed each other approximately
1500 feet above the ground.

The US Airways aircraft was equipped with a Traffic Alert
and Collision Avoidance System (TCAS) that issued climb
instructions to the crew to avert collision. The Beech 99
was not equipped with TCAS and the pilot was unaware of the
proximity of the Airbus. There were no reports of damage or
injuries as a result of the incident.

NTSB and FAA investigators conducted a preliminary
investigation at the Minneapolis airport traffic control
tower on September 18th and 19th and are continuing to review
the circumstances of this incident.

 

[gismo]

Sounds like they were IFR and in the soup.

Yep.
On a side note, I'm curious as to the "50-100 ft" separation that's been reported. Given that we all know that transponders report the nearest 100 ft of pressure altitude, and that there obviously is some error in any encoder, not to mention that both planes were likely climbing rapidly at the time and the radar records the transmitted altitude only once every rotation of the antenna (which take several seconds each), I can't see how transponder returns could provide any such range of separation.

I don't know what the FAA specs allow for the instantaneous error of the encoder/static system when an aircraft is climbing at several thousand feet per minute but I'll bet that if such a spec even exists it's at least a hundred feet or more. And even if you ignore that, by looking at two in-spec encoders fed by the same exact unchanging pressure they could read 100 ft apart if one transitioned to the next code just above the current pressure and the other just below it. Based on that and a plausible opposite direction 20 ft error in each encoder a difference in the mode-C of 200 ft could mean as little as 60 ft distance between static ports to as much as 340 ft. Combine that with the other error sources I stated and the worst case might be as much several hundred feet and an RSS error of at least half that. Of course the actual separation between parts of the airplanes would be lessened by the distance from the static ports to the vertical extents of the planes.

Seems these folks were mighty lucky indeed.

 

[roncachamp]

My understanding (weasel room here) is that depends on the class of airspace. In Class B ATC is repsonsible for separation of traffic in the airspace - that's why you can fly VFR in Class B only remaining "clear of clouds". In Class C and D it's only separation on the runway - and consequently the rules for cloud clearance are no different than normal VFR.

No, in Class C airspace IFR aircraft are separated from VFR aircraft.

 

[gismo]

No, in Class C airspace IFR aircraft are separated from VFR aircraft.

JOOC, who would you say has that responsibility for departures (inside class C or B) before the pilot is handed off to departure control, the tower or the radar room? I'm under the impression that the initial heading and altitude are assigned by the TRACON and the tower simply relays these to the pilots, is that correct? And if LOCAL properly instructs the pilots per the directives from TRACON and the pilots follows those instructions to the letter, could LOCAL be at fault for any ensuing deal?

 

[roncachamp]

JOOC, who would you say has that responsibility for departures (inside class C or B) before the pilot is handed off to departure control, the tower or the radar room? I'm under the impression that the initial heading and altitude are assigned by the TRACON and the tower simply relays these to the pilots, is that correct? And if LOCAL properly instructs the pilots per the directives from TRACON and the pilots follows those instructions to the letter, could LOCAL be at fault for any ensuing deal?

Where traffic is high enough to warrant Class C airspace it's generally too high for departures to be individually coordinated between tower and radar room. So Standard Operating Procedures are developed and adhered to. Such as standard departure sectors dependent on runway configuration; tower assigns headings within the departure sector and the radar room keeps arrivals out of the departure sector.

 

[Dr. O]

When the guy inn the jet can hear the racket from the prop plane over his noise in the cockpit, it's too damned close...
I agree with the analysis that mode-C update is in hundred foot increments and on a sweep schedule and with one plane climbing several thousand feet a minute that they could have been several hundred feet apart both vertically and laterally...
But given the pilot in a plane with the engines running at climb power still heard the props on the Beech, my bet is they came within a few tens of feet of swapping paint...

 

[JesseD]

Last night and this morning the news media has been busy reporting on a real near collision between an Airbus 320 passenger flight and a Beech 99 cargo flight. The Airbus departed 30R about the same time as the Beech took off from 30L (as cleared by the tower). As usual the reports are sketchy and confusing but it sounds like the tower expected the Beech to turn sooner than it actually did and based on that expectation had turned the Airbus into the path of the Beech. Somewhere it was stated that the Airbus got and responded to a TCAS alert (the reports indicate the Beech wasn't TCAS equipped although I was under the impression this was required for that size airplane) and it sounds like the Airbus passed over the Beech with about 100 ft of separation or less.

Wow. That would have had me changing my shorts.

 

[silver-eagle]

Wow. That would have had me changing my shorts.

And they said there was no damage...

 

[flyingcheesehead]

Yep.
On a side note, I'm curious as to the "50-100 ft" separation that's been reported. Given that we all know that transponders report the nearest 100 ft of pressure altitude, and that there obviously is some error in any encoder, not to mention that both planes were likely climbing rapidly at the time and the radar records the transmitted altitude only once every rotation of the antenna (which take several seconds each), I can't see how transponder returns could provide any such range of separation.

I don't know what the FAA specs allow for the instantaneous error of the encoder/static system when an aircraft is climbing at several thousand feet per minute but I'll bet that if such a spec even exists it's at least a hundred feet or more. And even if you ignore that, by looking at two in-spec encoders fed by the same exact unchanging pressure they could read 100 ft apart if one transitioned to the next code just above the current pressure and the other just below it. Based on that and a plausible opposite direction 20 ft error in each encoder a difference in the mode-C of 200 ft could mean as little as 60 ft distance between static ports to as much as 340 ft. Combine that with the other error sources I stated and the worst case might be as much several hundred feet and an RSS error of at least half that. Of course the actual separation between parts of the airplanes would be lessened by the distance from the static ports to the vertical extents of the planes.

Seems these folks were mighty lucky indeed.

It's not the radar thing that has me thinking "Holy ****" it's the fact that they *heard* the other plane, while at full power. That was CLOSE.

 

[Greg Bockelman]

it's the fact that they *heard* the other plane, while at full power.

I ALMOST have to call Blowing Snow on this.

 

[mikea]

Imagine if there had been a MAC, how the usual fix-short-of-a-wormhole would go, being that the airliner did have TCAS: "No propeller-driven airplanes may be within 10 miles of any jet airliner at any time."

Mandate TCAS XXV where the TCAS can engage and control the autopilot to do the avoid maneuver by computer control. Then in 2016 SkyNet became self-aware.

 

[bobmrg]

Why the near-simultaneous takeoffs on parallel runways? Seems to me that one or the other could have waited fifteen seconds.

Bob Gardner

 

[TangoWhiskey]

Why the near-simultaneous takeoffs on parallel runways? Seems to me that one or the other could have waited fifteen seconds.

Bob Gardner

That's a good question, something they could fix with an operational procedure. Do they have different controllers working opposite sides of the airport at MSP like they do at DFW? At DFW, I often hear "expect a short delay from a departure on the west side", and less frequently "expect a short delay for departures from Love" (the latter mainly during bad weather with increased spacing).

 

[nddons]

If they were that close, both climbing, wouldn't one or the other have reported major wake turbulance?

This one will be interesting to read about.

 

[texasplt]

Mode S transponders can report altitude with 25 foot resolution. All transponders are not limited to reporting altitude in 100 ft increments.

Aircraft with less than 30 passenger seats are not required to have TCAS II installed.

 

[jesse]

If they were that close, both climbing, wouldn't one or the other have reported major wake turbulance?

This one will be interesting to read about.

Depends how they pass each-other but it's very possible for there to be no wake turbulence even though they may have gotten incredibly close.

 

[Greg Bockelman]

If they were that close, both climbing, wouldn't one or the other have reported major wake turbulance?

If one went directly over the top of the other...

 

[flyingcheesehead]

If they were that close, both climbing, wouldn't one or the other have reported major wake turbulance?

If one went directly over the top of the other...

Bingo - Wake turbulence is more behind an airplane than below it. Plus, I'm guessing that even if one did fly through the other's wake that if the Beech was higher that the bigger bird wouldn't have been able to tell. If it would have even moved the big bird, such a small bump wouldn't have been able to be distinguished from regular in-the-clouds turbulence.

 

[nddons]

Bingo - Wake turbulence is more behind an airplane than below it. Plus, I'm guessing that even if one did fly through the other's wake that if the Beech was higher that the bigger bird wouldn't have been able to tell. If it would have even moved the big bird, such a small bump wouldn't have been able to be distinguished from regular in-the-clouds turbulence.

If a jetliner is climbing, the wingtip votices coming off the wingtips would be well below where the aircraft was 5 seconds ago or 10 seconds ago due to the steep climb gradient.

Could the Airbus pilot hear the Beech if it was below the Airbus? What if it was 100 ft off its wing? Just wondering. Like I said, the story will be an interesting read, not unlike the airliner that just left SFO and had a near miss with a 182, if I recall. One of the pilots of the jet told the tower something like "We need to talk."

 

[weilke]

Why the near-simultaneous takeoffs on parallel runways? Seems to me that one or the other could have waited fifteen seconds.

For landings, I believe KMSP uses a precision runway monitor procedure to land 30L and 30R at the same time. Pretty neat to watch out of the side window of a commercial flight if another plane breaks out of a layer at the same time and same altitude just 1/2 mile offset. They also take off at the same time but both planses usually turn away from each other right after takeoff.

 

[Greg Bockelman]

If a jetliner is climbing, the wingtip votices coming off the wingtips would be well below where the aircraft was 5 seconds ago or 10 seconds ago due to the steep climb gradient.

Yes they would. Doesn't change the fact that if one was right on top of the other, vortecies from the higher one would not affect the lower one.

Could the Airbus pilot hear the Beech if it was below the Airbus?

I doubt the Airbus guys could hear the Beech. But I kinda sorta think the Beech could hear the Airbus if it was as close as they say.

What if it was 100 ft off its wing? Just wondering.

Don't know. I don't think so.