How useful is an NMA?

The usefulness of an NMA

The usefulness of the NMA will be defined by its capacity, range and operational economics. We have through our performance model a good handle on the economics and through our airliner cabin knowledge, we can configure realistic operational cabins. We also know the range consequences of real airspace routings and the effects of weather on flights.

The question is then. After developing a real practical range for the NMA, what city pairs can it serve and with what operational result? This will be our subject in a series of articles.

The practical range

The first thing we need to understand is, what will be the practical range of the NMA and what routes can it serve. We will start with the range.

When an OEM tells airlines an aircraft can fly 225 passengers over a route range of 5,000nm (or 265 passengers 4,500nm)  there are several factors to consider:

  • The aircraft is configured with a nominal cabin without options. When an airline has chosen a cabin with its options (Avionics, Seat types, IFE, Internet access, Galleys and other options) the airliner takes fewer passengers and its empty weight has increased.
  • The nominal range is for a new aircraft with new engines. In service, the actual range deterioration can exceed 5% for the worst individual (called a tail) in the fleet. Routes have to be designed for the least capable aircraft, otherwise, tail number tracking has to be employed and certain aircraft cannot fly certain routes. No airline wants this added operational complexity.
  • The routes have to be reliably flown the year through. Prevailing winds can reduce the range with up to 10%-15% on a bad day.
  • When the weather gets bad, the alternates will be further from the destination airport. The nominal 200nm alternate will not be sufficient, the reserves for the mission will increase. Both these points decrease the route distance which can be put in a winter schedule.
  • For some OEMs the assumed weight for a passenger with bags is unrealistic. For the Boeing STANDARD ruleset, this is not the case. There is no range deficit when applying realistic pax+bags weights to the NMA.

Working in the opposite direction is the real-world load factor. Nominal range is calculated with a 100% load factor. This is not realistic, not even for an LCC. Today’s load factors hover around 80% with a tendency to slowly climb.

On the other hand, the nominal range is calculated with no cargo. Cargo is a revenue bonus, even though its modest for an aircraft like the NMA. It uses the smaller container standard from the Airbus A320 series (LD3-45) and after passenger bags are loaded there will be limited cargo positions left.

To do a final judgment of the practical range we need to settle the empty weight change a practical airline configuration will bring. Most important is to define a realistic cabin with its options.

The practical cabin

When the rumours say the NMA has 225 seats, they describe an aircraft which is configured with the Boeing short haul cabin defined in the STANDARD ruleset. This means about 7%-8% Domestic First-class seats at a 36-38-inch pitch, the remaining 92% being Economy seats at a 32-inch pitch.

Any non-LCC carrier will have at least 10% if not 15% business seats, combined with a Premium economy section and then Economy seats. The NMA is an eight to 10 hours trip time aircraft. Legacy carriers will install their typical lie-flat business seats, weighing four times more than a Domestic First-class seat and taking more space. And the Premium economy seat is twice as heavy as an Economy seat, once again taking more space.

The end result is a lower seat number and a heavier cabin. If we equip the 225 seat NMA with our Normalized long-range dual class cabin it will have 185 seats, and this cabin would increase the empty weight with 3.5 tonnes. The figures for the larger NMA is 215 seats and a weight increase of four tonnes.

The weight increase for a legacy airline NMA means a loss of useful range of around 500nm. Using realistic load factors for our missions we gain back most of this range loss.

The range we will use in our operational evaluation

The above factors mean we will have a shorter practical maximum range in everyday use of an NMA. We will use a practical maximum range where we don’t consider the effect of the wind and increased alternate distances. We will then take these factors into account dependent on the market/routes we study and their prevailing winds and weather.

The practical still air range for the smaller NMA we will put at 4,500nm and the larger at 4,000nm. For each market check on what type of routes it can serve we will factor in the local winds and prevailing weather at Origins and Destinations. We will also discuss the effect of any cargo payload.

To read the rest of the article Login or Subscribe today.