Maintenance - Page 12 Aviation Articles

Real World Impact on Aircraft Performance

Falcon 900EX Easy

The aircraft OEMs and sellers always seem to haver a war of words going on over “maximums.” Who has the fasted aircraft, the most range, the biggest cabin, the most headroom, etc?  When evaluating aircraft, you need to take the maximums into account, but critical is understanding the real world limits on those maximums.

Aircraft performance maximums can be very useful in comparing aircraft. Especially if you know the conditions they were assuming for the calculation. But be wary of translating the maximum to the "real world." This is especially true of range. Too many buyers get an aircraft that they believe can do the trip nonstop only to discover that "nonstop" has restrictions. They get quite upset when they end up with a fuel stop en route.

As pilots, we know and understand these restrictions, but many of the folks in the back fail to understand these, until after the sale. Better to educate them upfront than be accused of backpedaling after the fact.

The first thing that impacts the real world range is winds. In the Northern Hemisphere, prevailing headwinds run on a West-to-East pattern. So trips from Europe to the US have headwinds while trips from California to New York have tailwinds. Those winds vary seasonally and by altitude. 

Boeing publishes wind probability data for many of the common air routes in the US and worldwide. A common wind data point is the 85% Probable Wind. That means that the wind on that route will be no worse than that value 85% of the time. Here in the US, flying from the East Coast to the West Coast can have an 85% probable headwind of around 70 knots at 39,000 feet. So flying east to west, you should have 70 knots or less headwind 85% of the time for example.

Hawker 900XP


Last winter on an airline trip, we hit 135 knots on the nose for much of the Baltimore to Phoenix trip. Not sure, but think that was a 99.9% “Probable” wind leg. No aircraft can do the trip 100% of the time, but make sure the maximum range is suitable for your typical maximum trips. Here is a conservative shortcut that gets the job done.

When looking for that non-stop airplane, you factor in those probable winds as a reduction in cruise speed. If the route is 2,100 Nautical Miles (NM), that is across the ground. Headwinds effectively increase that required distance. If the aircraft cruises at 430 knots in a 70 knot headwind, its ground speed will only be 360 knots. Fly into this headwind for five hours and your trip has effectively increased by 350 miles - almost an hours' flight time. Looking at this another way, to fly that 2,100 NM trip in a 70 knot headwind requires an aircraft with about 2,450 NM range (with no wind).

Other things that reduce the fuel efficiency and thus maximum range of the aircraft:

  • Payload - heavier aircraft burn more fuel at a given speed and may require a lower initial cruise altitude until they burn off enough fuel to reach a higher, more fuel-efficient altitude. How many bags does the boss bring?
  • Temperature - on very warm days the aircraft may take longer to climb to altitude, or even require a lower initial altitude. Temperature may also effect engine-out departure restrictions.
  • Circuitous air routes - while airways routes typically add no more than about 3% to the straight-line distance, some routes may add more due to airspace restrictions or transoceanic routings.
  • Long, over-water trips may require alternate airports that are a significant distance away from your destination. This will reduce the available fuel load for the trip.
  • Poor weather over a large area may mean a circuitous route and may also require an alternate airport a significant distance away.


Factor in headwinds, heavy passenger loads, and a warm day and that 2,100 NM trip may not be non-stop anymore. So if you are looking for 2,100 NM nonstop trip with high-probability, you may be looking for an aircraft that has 2,600 NM range with your anticipated payload. In this case, a 2,600 NM maximum range is a valid requirement. 3,000 NM range is nice, but 2,600 NM will do the trip 99% of the time.

When evaluating aircraft, the maximum ranges, maximum speeds, payload capability, etc. can all be important considerations. But when you are looking at specific trips, you need to factor in some real world considerations appropriate for your trip conditions.

 

Gulfstream G450

Three Reasons For Having An A&P On Staff

If you are busy, here’s the condensed version: If you operate a turbine business aircraft and reliability is a key metric, unless you have 24/7 maintenance on the airport, you need an A&P on your staff.
If there is a service center at home station and they provide quality service and are knowledgeable about your aircraft model, it can be cost effective to have the service center perform the maintenance rather than employ a full-time maintenance person. Especially if that service center operates around the clock, or close to it. If you don't fall under that scenario, here are three reasons for having an A&P on your staff.
No one knows your aircraft better than your own A&P. That person gets to know the maintenance that was performed, the issues that the aircraft may have had in the past, and who/where to get the answers when maintenance questions arise. This is important in keeping the aircraft reliable and ready for flight when needed.
The in-house A&P understands your mission. Being your employee, she is fully dedicated to keeping your aircraft airworthy and safe. You will not get a better level of service than having a great employee as your A&P. They can earn back their salary in getting one critical mission off the ground on time.
When your aircraft is in for heavy maintenance, you're A&P is also your advocate in keeping the aircraft maintenance on time and within budget. While a good service center makes every effort to get the job done on time, the personal attention from your A&P will make that much more likely to happen.
The older and more complex your aircraft, the more critical it is to have the A&P on your staff. As with any aircraft, there may be minor issues that can delay your departure. The A&P being immediately available will enable a high level of dispatch reliability. In-house maintenance staff gives you the dedicated response on your schedule and is there to serve just you.
One of our clients has a 30+ year-old twin turboprop. Their limited budget includes a skilled A&P. Their dispatch reliability is in excess of 95% and their downtime due to unscheduled maintenance is far lower than you'd expect from an old aircraft. The maintenance manuals for their plane have notes and annotations representing the years of accumulated knowledge on how to maintain their aircraft. In these and many other cases, having the A&P on staff provides a level of skill and knowledge that enables the operator to maximize the utility of their aircraft.
I've heard from a number of operators that their A&P's salary was paid for at the first major inspection. Having the A&P on staff is cheap insurance for an on time departure. This further enables the executives to conduct their business in the most efficient manner.

Sierra Industries receives Mexican government DGAC approval for aircraft inspections, service and modifications


UVALDE, TX – April 20, 2012 – Joining a select group of approved aircraft service centers in the United States, Sierra Industries has been certified by the Mexican government aviation agency to service Mexican-registered aircraft. The Dirección General de Aeronáutica Civil (DGAC) presented certificate no. CO-038/12 to Sierra Industries representatives on April 4, permitting the company to inspect, repair and modify a wide variety of aircraft from piston singles to cabin-class business jets.

In May, the Mexican government is expected to issue a ruling restricting maintenance services for Mexican-registered aircraft to facilities located within Mexico, with the exception of a limited number of DGAC-certified facilities outside the country’s borders. Located some 50 miles from the Mexico-Texas border and less than 250 miles from Monterrey, Sierra’s Uvalde facility is ideally positioned to allow convenient access to Mexican-based aircraft.

Enjoying nearly 30 years of aircraft service and modification experience, Sierra Industries’ location at Uvalde’s Garner Field Airport offers true “one-stop shop” capabilities including PMA parts manufacturing. in-house avionics support and on-field paint and interior specialists. Numerous Sierra employees are bilingual in Spanish and English, helping to facilitate communications with south-of-the-border aircraft owners and operators.

A number of Mexican-registered aircraft already enjoy one or more of Sierra’s well-known Citation performance modifications, such as FJ44 re-engining and Eagle/Longwing airframe upgrades. The DGAC certification ensures that those owners can continue to utilize Sierra’s expert service for their upgraded aircraft and new modification clients can count on after-the-sale support without undue regulatory restrictions.

For more information, please contact me at your convenience.

   Jim Gerrish
   Manager of Creative Marketing
   Sierra Industries, Ltd.
   830-278-4481 ext. 226

Guaranteed Maintenance Plans 101

 

I drive my Honda Odyssey about 25,000 miles per year. I’ve done the maintenance on schedule and save for brakes and tires, that is all that it has needed these past few years. No unscheduled maintenance! That’s why I like my Honda. 

Unlike my Honda, aircraft have some very complex systems. Those systems cost far more than my Honda, and an unscheduled event outside of warranty can be costly. Even the scheduled maintenance can be expensive, especially for things such as C-Checks, 12-year inspections and of course, the engine overhaul. 

Turbine airplane manufacturers and one third-party company have tried to take some of the pain away from the maintenance budget and offer some peace of mind with Guaranteed Maintenance Programs (GMP). Here is a primer on these plans.

What are they? As the generic name suggests, these plans are a way to contractually guarantee your maintenance costs. You pay an hourly accrual fee to the plan vendor. That money goes into a reserve account. When maintenance is due, the plan vendor pays for the maintenance. Costs are guaranteed with no major spikes for costly inspections and overhauls. The resale value of the aircraft is enhanced by the dollars accrued in the program, by the guarantee of cost coverage, and by the quality maintenance records these programs require of the operator. 

Along with the financial stability these plans offer, many financial institutions are looking for these programs to secure the value of the aircraft under a loan or lease, especially for the engine coverage.

The history of these plans has its start in the airline industry. When making huge fleet purchases, the deal was sweetened by the engine manufacturers when they offered guarantees on engine costs in order to secure the selection of their engine. Today each major turbine engine manufacturer has some sort of GMP for their engine

In addition to the large turbine engine companies, many of the business airplane manufacturers and Jet Support Services, Inc (JSSI), an independent company, provide these GMP. JSSI is the only major third-party provider of turbine GMP for business aviation.  The engine companies cover their respective engines. The airframe manufacturers cover their airframes and several of the major avionic manufacturers cover their avionics. JSSI covers turbine engines, APUs, and also has programs for many of the newer airplanes’ airframes and avionics.

These companies have an extensive staff of trained maintenance professionals who work with you and the maintenance providers in order to secure both a competitive price and to make sure the vendor does the job in the best possible manner. 

What kinds of maintenance are covered?  These plans tend to cover the scheduled and unscheduled maintenance (except negligence).These plans can cover the engines, the airframe, avionics, or a combination of all three. The most popular seem to be the engine plans (also called power by the hour (C) by Rolls-Royce). Most turbine engines are covered by a GMP for the engine, either by the manufacturer or by JSSI. 

Engine plans typically include parts and labor. Optional coverage can include rental engines.  Airframe plans typically cover the airframe parts. Labor coverage is rare. Part of that may be due to operators having their own in-house maintenance staff. Tracking in-house labor required under a guaranteed plan may not be feasible.  The part coverages are much like the engines covering scheduled and unscheduled part replacement. 

Avionic coverages may or may not be included in the airframe programs. They can get very specific depending on what avionics are installed. 

The GMP can sometimes be tailored to the operator’s specific needs. For example, if the operator is leasing a plane for five years, they may be able to get airframe/avionics coverage for the five year term plus reserves for the engines. 

Best when new! These programs are available on most popular turbine business planes and on some helicopters as well. They are offered at reduced rates to new aircraft buyers. Part of this is to encourage participation, part is due to the warranty coverage of new aircraft, and part is when accruing for maintenance, costs are lower for  younger aircraft. Aircraft buyers are encouraged to sign up early by the reduced rates for new aircraft/engines. Operators of older aircraft/engines can buy into the program, but often at a substantial cost if the aircraft or engines have accumulated many hours. 

Financial professionals love these programs as they offer a stable, predictable cost for maintenance. They’d rather pay $500 per hour for every hour flown than face a half-million dollar maintenance bill every couple years. They also like the insurance against unscheduled maintenance. 

GMP aren’t for everyone. Operators of older aircraft that are not on a program may not be able to afford the buy-in. For them, the engines can be covered if they sign up at engine overhaul, but they still may face a higher expense as they accrue for the higher cost of the second or third overhaul. Fleet operators with significant in-house maintenance may feel they can manage their fleet for a lower average costs. And some operators would rather keep their money until the expense occurs rather than let the GMP provider accrue the money in advance. 

A GMP can add value and provide peace of mind to the aircraft owner. They warrant careful consideration, especially for the new aircraft buyer.

 

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