Completing the Circle

Completing the Circle

Completing the Circle

An Accident Analysis & What We Can Learn From It.

The May 2017 crash of a Learjet 35 at New Jersey’s Teterboro Airport has much to teach us regardless of what we fly. The National Transportation Safety Board reports:

 

The IFR flight plan to TEB planned a 28-minute flight at Flight Level 270. After departure about 1504 (local time), the flight was cleared to climb to 4,000 feet. The flight reached a maximum  altitude of 4,000 feet MSL. About 1515, the flight was cleared to  descend to 3,000 feet. The New York Terminal Radar Approach Control (TRACON) cleared the flight for the TEB ILS Runway 6 Approach, circle to land Runway 1. TRACON instructed the flight  contact TEB Tower about nine miles from the airport; however, the flight did not check onto the tower’s frequency until four miles from the airport. ATC cleared the flight to land on Runway 1 and issued the TEB winds of320 degrees at 16 knots, gusting to 32 knots. 

The flight did not start its right circling turn until it was less than 1 mile from the approach end of Runway 6. According to the tower, aircraft typically start the right turn at the final approach fix, which is located 3.8 nm from the approach end of Runway 6. 

A TEB controller observed the airplane bank hard to the right and he could see the belly of the airplane with the wings almost perpendicular to the ground. The airplane then appeared to level out for just a second or two before the left wing dropped, showing the entire top of the  airplane. Other witnesses also reported that they observed the airplane in a right turn with the wings in a high angle of bank. Some witnesses described seeing the airplane’s wings “wobbling” before the left wing dropped and the airplane descended to the ground. Security video cameras installed at numerous commercial buildings also captured the last moments of the flight, showing the airplane at high angles of bank. One security camera showed the airplane in a steep right wing low, nose down attitude at impact. 

There are many lessons promoted by this event, two specifically I want to draw from this example. The first comes from the NTSB excerpt above. 14 CFR 91.175 tells us that flight below Decision Height (DH), Decision Altitude (DA), or apropos to the Learjet’s circle-to-land maneuver, Minimum Descent Altitude (MDA), is permissible only when “…the aircraft is continuously in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent using normal maneuvers….” (emphasis added). 

Although “normal maneuvers” is not defined, banking excessively in the traffic pattern is not usually considered “normal.” The need to bank so steeply should prompt the pilot(s) to level the wings, then execute the missed approach procedure as applicable to the aircraft’s current location in the circle-to-land maneuver.

Lesson 1

The first takeaway from this report: Keep bank angle shallow close to the ground, even (especially) if in a circle-to-land or other visual maneuver. If your flight path, the wind or any other factor would require a steep bank or other unusual maneuver to establish or maintain alignment, use that need as a prompt to break off the approach—using normal flight maneuvers.

Lesson 2

Media commentaries about this re—port centered on crew qualifications, especially that of the First Officer.

The NTSB docket (detailed report) states:

Within the [aircraft owner’s] operation, SIC [Second-in-Command] pilots were ranked on a 0 to 4 scale and restricted as to the type of flying they were allowed to perform so as not to overwhelm them before they were ready. In order to be allowed to fly as SIC on empty legs [positioning flights], the right seat pilot of the accident aircraft would have been required to hold a rating of SIC-2. On the day of the accident, he was rated as a “0” and as such should not have been [Pilot Flying] of the aircraft at any time.

Both the Captain and the First

Officer appear to have been qualified for their respective roles, at least as far as the FAA is concerned. The “0-4” rating scale discussed in the NTSB docket is a company policy, not an FAA rule…unless, perhaps, it is written into the charter operator’s FAA-approved Operations Specifications (OPS-SPEC), and that OPS-SPEC was required to be in force not only while the carrier engaged in Part 135 (charter) operations but also when on positioning flights between passenger-carrying gigs. 

This brings us to the second takeaway from this example: personal minimums are only useful and valid if we adhere to them all of the time, not just when it is convenient. The charter operator’s SIC rating session is essentially the same as a personal minimum any operator (or individual pilot) might put on him- or herself.

I’ve been tempted to land with 45 or 50 minutes of fuel remaining on board instead of my personal one-hour minimum. I’ve looked at a cloud layer just a little below circling minimums for the runway in use, and really wanted to take off. I’ve had to fight off a “go” mentality for a late-day departure when I’ve been awake for more than 12 hours. Yet, each one of these flights are perfectly legal. The limitations are my own – my personal minimums. 

You probably have some personal minimums of your own. They come from your own experience – something you did or did not do, and you learned better – or from reading or hearing the experiences of other pilots. Personal minimums are a very good thing. But you have to use them even when you don’t want to. In fact, that’s the whole idea of personal minimums. They’re the voice of reason and logic, when you’re most tempted to make decisions emotionally, often when you have insufficient information with which to choose. 

I’m pretty sure the Learjet pilots’ employers would have made its “0-4” rating rule clear to the pilots in their new-hire training and when upgrading to Captain. The pilots probably knew better than to do a lot of what it appears they did that inexorably led to their deadly loss of control. If the crew had only followed the two limitations, one regulatory about maneuvers below MDA, the other personal, the company OPS-SPEC requiring the Captain to fly the approach, that decision might have been enough to save their lives and prevent all that destruction.

Accident causation has been likened to a chain of decisions or a chain of events. It has also been modeled as layers of Swiss cheese: Each layer is the chance to block an accident path, if the “holes in the cheese” don’t line up. All it takes is to break a critical link in that chain or to move the cheese: to make and act on a decision that manages the risk to prevent a crash. Personal limitations are your means of reversing trends that might lead to an accident. Just follow the rules – the FAA’s and your own – and you probably won’t get hurt.

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Visual or IFR?

The TEB tower controllers mentioned that previous aircraft started the circle at 3.8 miles. This is outside the obstacle-protected area for any category aircraft. This fact raises the question: is it now a visual approach? Are all circling maneuvers visual?  

Assuming the Lear 35 approaches at CAT C (121-140 knots ground speed) or even CAT D (141-165 knots ground speed), then beginning the circling portion of the maneuver about 3.8 nm from the runway would not be authorized. It would be if the Lear was flying at 166 knots ground speed or greater, but I don’t think even a Lear 35 is routinely that fast in a circle-to-land maneuver.

Conditions at the time of the accident were 5,500 scattered, visibility 10 miles; in other words, good VMC. Therefore: 

If ATC cleared the flight for a visual approach, the pilot could (and probably should) have maneuvered to align with Runway 1 farther from the airport than he did.

If ATC cleared the pilot for the circling approach, even though that portion of the flight was in VMC, the pilot is obligated to adhere to the circling altitudes and radii to comply with that clearance. That said, the pilot is also required to miss the approach if he/she cannot descend below Minimum Descent Altitude (MDA) using “normal maneuvers,” which is not strictly defined but using a “reasonability test” does not include low-altitude near-knife edge maneuvering like the accident airplane was observed to do.

The circle-to-land portion of a circling approach must be done with visual contact with the airport, but conditions do not have to be VMC, only the minimum visibility published for that approach and clear of clouds. It is an Instrument Flight Rules procedure that requires outside visual contact to perform. So, the circle-to-land maneuver is a visual procedure, but not a VFR procedure. 

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Circling Radii: Not What You Might Think

The rules about protected airspace in a circle-to-land maneuver are probably different than you learned when you earned your instrument rating or ATP. Since 2012, the radius of the protected area centered on the ends of the runways changes with changes in altitude above Mean Sea Level. 

Although the circling radius is based on the aircraft’s ground speed, this takes into the account the higher True Airspeed for a given indicated airspeed at a higher altitude. It may seem academic (after all, even longer radii than you originally learned apply at higher elevation airports), but the “most correct answer” is no longer a single protected airspace radius for each approach category listed on an instrument approach chart.

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