Preventing Another Hudson Midair

By Robert Mark on August 14th, 2009

Although the people at Fox News have always been very nice to me when they call and ask for my technical expertise on aviation matters, I must admit I do sometimes dread their calls. That’s because their phone calls usually means something bad has happened, as it did when they rang me last weekend about 10 minutes after the helicopter and the the Piper PA-32 ran together over the Hudson River.Garmin Traffic - jetwhine Nine people lost their lives. The amateur video of the crash made the point that pilots simply looking out the window to avoid other aircraft doesn’t always work.

No surprise too when plenty of people began pointing fingers of blame at, the helicopter pilot, the Cherokee pilot, the air traffic controllers at Teterboro Tower – who were yesterday suspended in fact – and this somewhat unregulated look to air traffic in the New York area. And let’s not forget that folks in the New York area are highly-sensitized to things flying over their heads, and with good reason too.

Perhaps it won’t be this accident alone that causes a change, but eventually more intense air traffic demands will force the industry’s hand.  I also gave a radio interview about the future of collision avoidance to WRHU in New York on Tuesday. My friend Max Trescott and I were also talking last night how the accident could have been prevented and came to very much the same conclusion. A traffic avoidance system based upon transponders – transponders are already required in this airspace – might very well have prevented this tragedy. The business jets I fly – as well as all airliners – are required to carry such gear. Small aircraft are not, at least not yet.

The picture above (courtesy of Garmin) shows you the kind of screen I also see in the Cirrus SR-22 that comes equipped with a basic mode of traffic avoidance software. Of course, every aircraft is not a glass panel like this, but there are less complicated versions of traffic avoidance equipment available as a retrofit in all aircraft.

How Traffic Avoidance Systems Work

Essentially, a good TCAS system searches for other aircraft with air traffic control transponders. That equipment already tells controllers on the ground about the direction and aircraft is moving, as well as its altitude. TCAS systems simply analyze this information in a way that’s more useful to pilots in the air, especially those who might NOT be in contact with ATC.

If that had been me in the airplane last Saturday with the helicopter closing from my blind spot, the traffic avoidance system would have started warning me 30 seconds before impact to tell me there was something about to happen that I might yet prevent. It would have sounded like this to the pilot. If both the helicopter AND the Piper were so equipped, both pilots would have received the alert.

In this photo, the big yellow circle on the Primary Flight Display above would be the visual representation of the approaching intruder. A tag attached to the yellow dot also tells me the altitude of the intruder reference my aircraft … – 200 means the aircraft is currently 200 feet beneath my altitude. Plenty close for sure, but not dead on. If the altitude read showed “00” that tells both pilots the other aircraft is at exactly the same altitude and that a midair is imminent. The traffic dots give any pilot a chance to take action, such as turn away. As the traffic conflict gets closer to a collision point, the yellow dots will turn red and repeat the traffic alert.

Larger aircraft also include an added element of sophistication called resolution alert. On board an airliner or a business airplane, the computer will give the pilot the best route to take to avoid a collision, a particularly helpful tool when time is short. In this case, the aircraft is being told to change altitudes and it sounds like this.

Although all large aircraft carry traffic avoidance equipment, it is not yet required on small aircraft. My guess is that in the New York area, and other larger metropolitan centers this will soon become required … and it should.


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9 Responses to “Preventing Another Hudson Midair”

  1. RobM Says:

    Good post except.. even if TCAS is made mandatory in light aircraft, helo’s would probably be exempted as they’re exempted from so many other things like this because of their mobility.

    However, not to pick a bone, but TCAS only issues resolution advisories as climbs or descents. No turns. Sometimes…. many times… a turn is the better conflict resolution but as far as I know, the current TCAS system cannot or will not even calculate that.

    This was an unfortunate but completely foreseeable incident. Moderate to high volume of VFR traffic, stuck below busy IFR airspace and hemmed in by other airspace/city . These pilots should have been on super-high alert and unfortunately, a bad mix of a climbing helo and a level cherokee makes see and avoid very tough.

    I feel for the controller.

  2. Robert Mark Says:

    Your points about TCAS are very accurate Rob. A turn is often the best solution, but as you said, the technology is not there yet.

    That was the saddest part of this accident is that the chances of either of these two pilots ever seeing each other from the angle they hit was almost nil.

    Collision avoidance is coming. I remember when a 172 and a 727 ran together in southern California – probably 30 years ago – and killed everyone.

    The TCAs came to be after that … and one more ugly midair. This is probably evolutionary in crowded airspace.

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  4. Wes Hartley Says:

    I think this accident was tragic and might have been prevented if several other things might have happened, but does this one accident really require new regulations to be written?

    I think we may have lost perspective…hundreds of people die every day in auto accidents. There are regulations for speed, sobriety, lane usage, seat belt usage, airbags, and even the mechanical state of the automobile…and yet people (thousands every year) die in automobile accidents. Everyone knows where the dangerous stretch of road is in their neighborhood and they become more vigilant when they drive it. Should that road be shut down, or only specially equipped cars given access? No! There is an expectation that a driver will be vigilant, drive carefully, and assume the risk involved in driving that dangerous stretch of road or find another route.

    Again, I feel terrible that lives were lost in this accident, but it certainly does not merit mandating extremely expensive avionics that might (or might not) have helped prevent this accident. Flying involves risk and reward….as a pilot, I have to decide if the reward of a short-cut or pleasure flight through the Hudson corridor is worth the risk that trip carries….

    I see no reason to mandate new equipment for pilots who have successfully and vigilantly flown in Bravo airspace for years.

  5. Bill Palmer Says:

    I have to agree with Wes, but it is encouraging to see that TCAS type systems are becoming available for light aircraft. I don’t think it’s time for mandating new expensive equipment.

    That this type of accident is as rare as it is over the Hudson corridor is a testament to how effective the current system really is. While the advances in technology will continue to make the situation safer, most of the proposals thrown out by the politicians would actually make things worse.

    I used to fly up that corridor as a new private pilot. The rules were simple: stay right, and watch for other traffic, because it IS there! And PLEASE folks, turn on those landing lights! They increase your visibility many times over – day and night. Airlines don’t have the lights on all the time below 10,000 because they like to buy light bulbs.

    Another technical correction (sorry)to add to RobM’s in regards to: “That equipment already tells controllers on the ground about the direction and aircraft is moving, as well as its altitude. ”

    Actually, the transponder does not send position and direction of flight info (yet). Instead, the TCAS unit determines the relative position of the other traffic by analyzing the tranponder signal’s relative position with a direction sensitive antenna and the time delay between interrogation and reply (essentially the same way ATC’s secondary radar works).
    TCAS systems can only generate Resolution Advisories (climb or descent orders) if BOTH aircraft have a TCAS system, since the maneuver is coordinated between the two systems – otherwise the best you get is a traffic advisory.

    A future system (just starting to be used in limited applications) is ADS-B (Automatic Dependant Surveillance – Broadcast), which will transmit a GPS position and other data that is received and displayed on other aircraft navigation displays.

  6. Keith Renz Says:

    “Airlines dont have the lights on all the time below 10,000 because they like to buy light bulbs.”

    Not sure where you got this from. (Assuming you meant, “… because they [don’t] like to buy light bulbs.”) The major airline I work for requires ALL exterior lights be ON below 18,000′. Everyone in Flight Ops, training, etc., enforces this policy. Safety is always first.

  7. Bill Palmer Says:

    That was exactly my point. Typing and speaking can carry different meanings. The statement was meant to be a little sarcastic. The “don’t” applied only to the desire to buy light bulbs as the reason.

    How about this: Airlines all have the lights on below 10,000 feet (or higher) , and it’s not because they like to buy light bulbs, it’s because it reduces the chance of a midair collision!

    Sorry for the confusion.

  8. Keith Renz Says:

    Bill, now I understand. Good point.

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