Using Big Numbers

Using Big Numbers

Using Big Numbers

Years ago, I was conducting recurrent King Air 200 training with the two experienced and professional pilots of a Midwest corporation. As part of their takeoff briefing, they used the phrase, “We’ll use big numbers.”

“What did you say?” I asked. “What does that mean?”

Their explanation made a lot of sense to me then, as it does now. It is a procedure that I have adopted and use regularly. I believe it adds a degree of safety that helps to stack the deck in our favor. With one very minor exception – that I will address later in this article – I can see no detriment or downside to it whatsoever. Let me explain.

Not all King Air models have differing takeoff speed numbers depending on conditions. The fine E90 model, for example, bases all of its takeoff data on using a rotate speed of 95 KIAS (knots indicated airspeed) and a 50-foot speed of 100 KIAS. Although Beech does not use the terms V1 and V2 for the E90 – reflecting its date of certification, its weight, and the rules that then applied – those two numbers would be the 95 and 100. These speeds apply to all airport elevations, all outside air temperatures and all weights. I much appreciate the simplicity they provide. Although they may not be “perfect” for all situations, the E90 is such a fine performer that it does very well using them in all situations.

As the King Air history evolved and the larger and heavier model 200 appeared – with first deliveries in 1974 – takeoff numbers became more elaborate. Although I have written and spoken about my disagreement with Beech’s choice of V1/VR for the 200, I have no problem whatsoever with their V2 choices. V2 varies from a low of 99 KIAS – while using approach flaps for takeoff at a light weight of 9,000 pounds – to a high of 121 KIAS – clean, at the maximum gross weight figure of 12,500 pounds. Similarly, the 300-series use a wide range of V-speeds that vary based on flap setting and weight.

Here’s the idea of “big numbers”: The day that I first learned of this technique – with the two pilots of the 200 in the Midwest – we were about to depart from an elevation of 800 feet, at 11,500 pounds, with an OAT of 20°C, and about an 8-knot headwind component. However, the crew – years before in the comfort of their hangar office – had worked out a lot of takeoff performance problems for their own home-base airport as well as other airports they frequently used. In all cases, they did the exercise based on worse-than-expected conditions. In this home-base case, they used 1,000 feet elevation, 45°C temperature, 12,500 pounds, no wind, no flaps. They found that both Accelerate-Stop and Accelerate-Go distances were less than the 8,000-foot runway they would be using.

If the airplane can perform satisfactorily using these worse-than-actual conditions, then is it not correct to believe that the actual performance will be better than (and certainly no worse than!) the performance numbers the POH provides even if we use the higher V-speeds for the higher weight? After all, we will reach those speeds in less time and our climb rate, using the higher V2, will be greater than the chart presents since we are at a lighter weight. As a side benefit, our margin above VMCA and VS will be greater than what the chart assumes, again due to our lighter weight. In effect, our margin for error is improved when “big numbers” are used. Even if we over-rotate and fall a bit below the “big number” V2, we may still be at or above the actual V2 for our real conditions.

The only detriment that comes with using the higher speed appropriate for a greater weight is increased tire wear, since we will be rolling on the runway to a higher speed. Personally, I am very willing to accept the slight extra maintenance cost, thinking the safety benefit it provides makes the cost worth it.

Last year, I was involved in transitioning a Phoenix-based flight department from their B200 into their newly purchased 350. The 350 had been extensively upgraded by Stevens Aerospace and Defense Systems (formerly Stevens Aviation) in Nashville as a part of the purchase. These upgrades included the Blackhawk XP67A engine swap and installing the Garmin G1000 NXi package … making a great airplane even greater! (This magazine had an article about that airplane and its owner/operator a couple of months ago.)

Being based at Cutter Aviation on the south side of Phoenix’s Sky Harbor Airport, the runway we were usually assigned was 7R – 25L, 7,800 feet long. Using the POH, as modified by the Blackhawk STC, I worked a takeoff performance problem using 2,000 feet Pressure Altitude (field elevation is 1,135 feet), 45°C OAT, 15,000 pounds takeoff weight (the maximum limit), Approach Flaps and no wind. Takeoff Field Length came out to be 5,672 feet, more than 2,100 feet less than what we had available. The “big numbers” associated with these conditions were 104, 105 and 109 KIAS for V1, VR and V2. My suggestion was to use these numbers for all of our KPHX takeoffs giving us a safety cushion, since rarely would all the variables conspire to be as bad as my assumed conditions.

As a side note: With the acceleration this rocket-ship of a King Air has, if the pilot can truly differentiate V1, VR and V2 he/she has better eyesight and reaction times than I!

As I write thwis (August 2019), my heart remains saddened by the tragedy that took place June 30 at KADS, Addison Airport in Dallas, Texas. A 350 crewed with two professional pilots and loaded with eight passengers crashed on takeoff, killing all souls onboard. I believe this is the first fatal crash involving a 350 in the United States. The King Air never left the airport boundaries, crashing into a hangar on the left side of the runway when it rolled inverted as control was lost. Speculation on the cause has been rampant. When the NTSB issues its final report, I pray it will present the correct, well-researched and reasonable cause that we can all accept. Meanwhile, I know this is a situation in which “big numbers” could have been used … that the actual conditions would have permitted it with margins to spare. Were they used? Would it have helped prevent the tragedy? We don’t yet know.

Before I close, I want to emphasize that all of the King Air models up to and including the 200-series are “light twins.” Only the 300-series fall into a category in which engine failure on takeoff needs to be officially considered. Although the POMs/POHs for the non-300-series do indeed present data based upon engine failures during takeoff, none of this is FAA-required information. Consider the E90 again. Just because it uses a V1/VR of 95 KIAS and a V2 of 100, should you always use them? I emphatically answer “No!” Using the long runways – 7,000 feet or more, for example – at most major airports, I would operate the E90 the same as I’d operate an Aztec or Baron or 414. Namely, I’d allow the airplane to fly “when it’s ready,” having lightened the nose with the correct amount of elevator force. There would be no definite, firm, sudden rotation. The landing gear would be retracted when at least blueline (VYSE) airspeed has been reached. Then the pitch would be raised to about +10°, knowing that if an engine does indeed quit this attitude will eventually yield a speed close to blueline. I would have the HSI’s heading bug set on runway heading and I’d be prepared to use my feet to “step on the heading” if I felt asymmetrical thrust. My briefing to the other pilot about engine failure would be, “If the gear has not started up, we are chopping power and stopping. If the gear has started up, we’re going.”

As I have said more than once recently in articles here, “Just because you can, doesn’t mean you should.” Treat a King Air’s takeoff like a FAR Part 25 Transport Category jet? In some cases, we can. But should we?

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