Comparative Field Lengths Jets and Turboprops

Business jets provide passengers with a level of safety during takeoff that is not found in the typical turboprop or piston-powered aircraft used in Business Aviation. But the terminology needs some explanation.

More than 5,000 airports in the US are not served by scheduled airlines. A business aircraft is productive partly because of its ability to land at many of those locations, which often are significantly closer to your desired destination. When selecting an aircraft, however, it is important that it be able to operate safely from the airport you selected.

Aircraft selection may involve choosing between a business jet and a business turboprop. A selling point in favor of the turboprop may be that its operating manual specifies less distance to take-off than a similar-sized jet. While correct in one sense, that specification can be misleading and confusing.

There are differences in operating regulations governing the two types of aircraft. For aircraft having a gross weight of 12,500 pounds and under, FAR Part 23 applies; Air Transport Category aircraft (i.e., those with a gross weight of over 12,500 pounds) are certified according to FAR Part 25. In particular, the philosophies behind these two regulations vary significantly.

FAR 25 vs FAR 23

The more stringent rules of FAR 25 provide greater safety margins over those deemed necessary for smaller FAR 23 category aircraft. (Business jets weighing 12,500 pounds or less comply with some of the conditions of FAR Part 25, such as runway length, but not all of the transport category criteria.)

These regulatory differences are the reason for the small turboprops’ reputation for being able to operate from shorter runways than small jets.

Take-off distance is the amount of runway required to take-off under full power. The FAR 23 requirement for runway length involves this calculation plus the distance to reach 50-feet (or sometimes 35 feet) in altitude. Required take-off runway length for FAR Part 23 aircraft has no allowance for either being able to stop on the remaining runway or to continue the take-off on one engine after an engine failure.

Most multi-engine turboprops certified under FAR 23 do include an additional calculation called “Accelerate-Stop” distance. This distance is the runway length required to accelerate to the normal take-off speed, identify a problem, abort the take-off and come to a complete stop. This is the runway distance  commonly used in discussing turboprop runway length requirements.

By contrast, FAR 25 intended for Air Transport Aircraft such as business jets and large turboprops (i.e. turboprops with a maximum gross weight above 12,500 pounds) assures that in the unlikely event of a problem during take-off, the aircraft can either:

•        Stop within the remaining runway length (Accelerate-Stop); or

•        Continue to take-off after the loss of one engine and climb on the remaining good engine (‘Accelerate-Go’ distance).

This calculation is called Balanced Filed Length (BFL). The limiting factor for the FAR 25 airplane is the distance required to take-off after the loss of one engine. Some FAR 23 airplane flight manuals do include this calculation even though it is not legally required.

Technically, BFL is the distance obtained by determining the “Decision Speed” (V1) at which the ‘accelerate-stop’ distance and the one-engine inoperative take-off distance are essentially equal. Decision speed is the speed of the airplane at which point the pilot decides to either continue with the take-off or slam on the brakes and stop the aircraft.

Runway Length Illustrated

To illustrate how these regulations work, let’s look at a typical situation involving a small turboprop (FAR 23) and a small business jet (FAR 25), both seating six passengers. We’ll assume maximum gross weight; sea level; outside air temperature of 59°F and standard pressure of 29,92 in.hg. (i.e., International Standard Atmospheric conditions); and a dry, level, hard-surface runway. The small FAR Part 23 turboprop can legally take-off from a 2,600-ft runway.

Let’s assume an engine fails at our example turboprop’s published rotation speed (Vr) of 94 knots. Rotation speed is the point when the aircraft starts to lift off the ground. Its distance to accelerate to Vr and stop is 3,400 ft, 800 ft longer than the take-off distance. If the take-off is continued after engine failure at Vr, then the runway required jumps to 4,750 ft (82 percent longer than the take-off distance of 2,600 ft).

Although 4,750 ft is the BFL for the turboprop, it is not a legal requirement under Part 23 for runway length decision. That extra distance required to provide a margin of safety should an engine fail at a critical time during takeoff, however, is significant.

The FAR 25 criteria include the accelerate-stop calculation. The small business jet has a BFL of 4,500 ft runway in the same conditions, 250 ft shorter than the turboprop under the same contingencies and with the same margin of safety.

Although the small business jet could take-off or accelerate/stop like the turboprop from a shorter runway, the pilot is not permitted to base the runway length decision on anything other than the BFL data specified in the aircraft approved flight manual.

As you can see, although the FAR 23 turboprops can legally take-off on shorter runways than most jets, FAR 23 doesn’t require the same safety margin as FAR 25. So when comparing turboprops with jets, you should recognize the additional takeoff margins required of aircraft certified in accordance with FAR 25.

 

ILLUSTRATED EXAMPLE:	FAR 23 Turboprop	FAR 25 Light Jet
‘Accelerate-Stop’ distance (FAR 23 required)	3,400 feet	Much less than 4,500 feet
‘Accelerate-Go’ distance	4,750 feet	4,500 feet
“BFL” (FAR 25 Required)	4,750 feet	4,500 feet
PUBLISHED NUMBER	3,400 feet	4,500 feet

 

Business Aviation By The Numbers

Aviation, like most highly technical fields, is dominated by numbers. The pilot must know the aircraft’s operating speeds, its weights, and the fuel required to reach the destination. The mechanic is concerned with safety tolerances, pressures, torques, and a myriad of other values. The aviation manager is responsible for the budget and should know the costs of maintenance, salaries, training, as well as the metrics of personnel management : the pilots, maintenance and support staff.

To the executive and Board of Directors, all these numbers are not important in their ability to manage and control the overall corporation. As a Director, you do not have the time to directly manage the aviation function, nor human resources, legal, marketing, etc. You hopefully have a talented team assembled whose jobs are to manage those functions. But, with all the recent attention paid to the corporate aircraft by the Wall Street Journal and the White House, you do need to  address whether the aviation function is adhering to the stated policies regarding the effective use of the aircraft.

Your corporation thrives on issues of profit and loss. You have a number of metrics that indicate not only the current profitability of your company, but trends and outlooks. While the corporate aviation function is rarely regarded as a profit center , metrics should be used to measure the function’s positive results as “profits” and identify trends that may lead to negative results (losses).

The aviation function is a service department and as such, service is a top priority (right after safety which should not need to be stated). Service quality can be hard to quantify, except for periodic survey’s among those serviced. But there are some other metrics than can be used to measure how effectively the aviation department is doing the job.

Budget versus actual expenses

The aviation department must operate on a budget and any variances outside the budget need documentation. Under the rule of “no surprises,” major expenses must be identified and budgeted for well in advance.

Cost Per Mile (running averages)

Aviation maintenance comes infrequently and sometimes with large costs. A running average of those costs should be available covering 12, 24, and 48 month intervals. The goal is to identify increasing cost trends over time.

Trips flown (compare to previous year’s activities if available).

This may include locations (by city, region and country as appropriate). The goal here is to ensure the aircraft is  being used where it is most beneficial to the business, or in support of major projects. Also, rapidly increasing activity may be a sign that additional aircraft may be needed later.

Denied Trip Requests: Trips unable to be flown (number and percent of  flown).

Is supply meeting demand? If the number of trips flown is increasing and trips denied is also increasing, then you may need more aircraft. The reverse trend may indicate under-utilization.

Dispatch Reliability

Dispatch reliability is the percentage of time a departure is made within a set amount of minutes of schedule. You can’t control the weather or the delays imposed by Air Traffic Control, but you can control the effectiveness of maintenance and the people who operate the aircraft. Delayed or missed trips due to unscheduled maintenance events should be extremely rare. If not, there is a problem. Also, a departure should never be delayed because the crew showed up late for work.

Aircraft Availability

This is defined as the amount of time an aircraft is available for flight (scheduled to fly or ready to be flown) compared to its normal operating year. For example, if the aircraft is normally scheduled six days per week, then its operating year is 6 x 52 = 312 days. If for 45 of those days the aircraft was not available to be flown due to maintenance requirements, then its availability is 86% (312-45)/312.  This number should be high. Decreasing availability typically is due to unscheduled maintenance.

Number of Months Since an External Safety Audit

Safety should be second nature and spelled out in the aviation department’s policies and procedures that you or another C-Level Executives have personally endorsed. A safety audit is an external validation of the safety culture and should be performed about every 24 months or less.

Number of rings before the phone is answered at the aviation department.

This is a bit trite, but worthy of consideration. The aviation function is a service function. The level of service in all areas should be high . Phones should be  answered by real people. Executives should not have to wade through a menu of options to talk to someone in the aviation department (to repeat this menu, please press 9). In place of counting phone rings, periodic surveys of the users asking “how are we doing” can suffice!

Corporations need the essential support of human resources, accounting and information technology. While their budgets may increase or decrease, their function remains the same.  The business aircraft fits into that same category – an essential business tool that is required for the efficient (and profitable) running of your company.

Measuring The Value of a Business Aircraft

While the majority of the Fortune 500 companies engage in Business Aviation, their reasons for having access to business aircraft may not coincide with your own reasons.

How do you justify the use of a business aircraft?

A rational, well constructed justification for employing Business Aviation is no longer an option. It is a necessity. It should be clear to your shareholders and others that the business aircraft is an essential business tool. One way to help in this approach is to have some means to support the value of the aircraft to your organization and enable you to state “Yes, our aircraft is an essential business tool without which our company would be a competitive disadvantage in today’s rapidly changing economic environment.”

With the inevitable change of Board leadership, someone will ask the question “Why do we have the aircraft?” There needs to be an answer.

There are many tangible benefits to having an aircraft. These include, but are not limited to:

• Time Savings
• Flexibility and Reliability of Operations
• Productivity
• Ability to attract and retain key personnel
• Ability to support customers in an effective manner

Some or all of these will apply to your situation. No one will deny the ability of the business aircraft to serve, but the question that still gets asked is “Are the benefits worth the cost?”

As an example, assume a trip is needed from New York City to San Antonio. Bus fare is $219, and the travel time, 50 hours. Via the airlines, you can make the trip in 5.5 hours flying, plus airport time, for about an 8-hour travel day. Business airfare for last minute travel may run $1,200 per person, or $4,800 for four persons. On the business jet, a charter may take less than 4 hours total time and cost may be about $10,000 for up to six persons.

No one will say that the bus is the “best value” way to travel, even though it is “cheaper.” However, many may question the value of the business aircraft. The business jet fee is eight times the airline ticket for a savings of “just” four hours. However, when evaluating the travel in greater detail, you may need an overnight stay (or two) at San Antonio versus having the ability to return late in the same day on the business jet. Furthermore, you can conduct business with your travel associates without concern that company business will be overheard by a stranger.

In order to determine the value of the business jet over the airline, you need to understand both the total time needed for the travel and the lost opportunity cost of that travel.

The business aircraft has but one master, you. It will travel on your schedule and thus, offers significant time flexibility. The airlines have set schedules in order to try and fulfill most travelers’ schedules. How can we compare the time and cost of both alternatives?

The National Business Aviation Association (NBAA) has a tool called Travel$ense . It is software that calculates the actual hours spent in travel, productivity advantages and trip expenses. Travel$Sense uses actual airline data to allow your travel specialist to compare the time it takes the business aircraft to complete your trip, and the time needed on the airline.. In addition to calculation the total travel time, it also has user-defined inputs for productivity and salary.

Using such a tool, you may calculate that the San Antonio trip takes 40 hours round trip on the airlines while the business jet takes 16 hours. But the next step is the critical one, the value of the time.

Time can never be saved. It can only be spent wisely.

In spending less time in airports and in airline seats, you can be more productive. However, you need to recognize some value to that time. In 1987 a company called PRC produced a study that looked at the benefits of business aircraft travel versus the airlines. It looked at both the tangible and intangible benefits. It then went a step further to try and assign a value (or cost) of the time spent (or not spent). It used business school research, industry data and insurance data to assign a salary multiplier to an executive’s time. The PRC study was further reinforced in 2001 by a similar study performed by Andersen Consulting that looked at the impact of business aviation on shareholder value.

While an executive is worth more than his or her salary, whether that value to a company is two times or five times greater is a subject for much discussion and controversy. A senior executive with a seven-figure salary and benefits package has to be worth at least $500 per business-hour to the firm. Business-hours spent in the office, with a client, or working somewhere quietly without disruption are more productive than business hours spent waiting at the airport. Whether it is Travel$ense or a spreadsheet, such an analysis can show that the time spent not traveling can be put to productive use, and that increased productivity can offset the added cost of using the business aircraft option.