“Compromise” in today's popular culture is largely a negative term. Something was given up to get something you want. But why not just get the things you want without the trade-offs?

Because the laws of physics don’t work that way.

Aircraft design is an endless flurry of compromise. Do you want an airplane that can fly long distances, operate from multiple airports, and deliver the lowest total cost?

Pick two.

In the past two weeks, Airbus has revealed much about the inevitable compromises it will very likely make on the A220-500. The stretched version the European manufacturer is considering includes a “simple stretch” with no new wing or engine platform.

Considerations had been made in the past for a new wing to better support a larger fuselage and a potential new engine. Neither is happening. Instead, the -500 will look a lot like a -300, only longer. It’s a simple stretch. So what compromises were made?

Firstly, the win: This airplane will be a seat-cost powerhouse. By our very simple estimates, the aircraft will deliver the lowest seat costs in the segment, handily beating both the A320neo and the 737-8. It will require a jump to the 737-9 or A321neo to deliver lower seat costs, but this requires the additional trip costs associated with carrying the incremental 40-60 seats to do so. We have a research report dedicated to the economics of the aircraft to be published to our clients this week.

Cool. Lowest seat costs. So, this means the A220-500 will replace the A320neo and 737-8, right?

No. Not even close, actually. We haven’t gotten to the compromises yet.

There are good reasons the stretch being considered has been described by Airbus as “simple.” As mentioned, no new wing and no new engine. New wings and engines are expensive. So why have them?

Because they tend to get you from point A to point B (well, more of you, anyway).

The A220-500, with the same wing as the A220-100/300 and the same PW1500G engine, will not exactly be a strong airfield performer. Not even close, by our estimates. In fact, the aircraft is what pilots would refer to as a “lead sled.” Doesn’t go up easily, but you should see it slide downhill!

No performance data exists on the A220-500 yet, and we know nothing from inside Airbus that isn’t public. What we do know is what the A220-300 can do, and we can estimate how a “simple stretch” of the A220-500 would perform.

For some reason, the most common A220-500 question we’ve been receiving over the past few weeks has been whether it will completely erase the business case for the 737-8 (and A320neo).

No. Final Answer. Please stop asking.

Here’s why: Compromise.

Keeping the same wing and same engine on a stretched A220 is cost-effective. Yes, there will be a reduction in range, but not as much as you would think (comparable to the 737-900ER vs 737-800).

But we tend to think of range independently of airfield performance. The “deep” analysis we usually read in the industry on aircraft performance rarely goes beyond the payload-range diagram.

How far could the A220-500 go? The answer: about 3,000 miles, give or take (with a healthy dose of assumptions, including identical fuel capacity to the A220-300 and sufficient MTOW [Max Take-Off Weight] and MZFW [Max Zero Fuel Weight] increases).

But that is the wrong question for a simple stretch such as this.

The better question to ask is how quickly that range drops when considering airfield performance. Besides, what good is range through the air if you can’t get off the ground?

And this is where the compromises of the simple stretch show their sneaky little faces. The A220-500 will be a seat cost monster… when it can use all of its seats.

If we consider no changes to the aircraft other than two fuselage plugs in front and behind the wing to match Airbus’s 180-seat claim, we have to consider the aircraft as mounting the PW1524 engine with 24,400 lbs of thrust. (By comparison, the 737-8 can mount two LEAP-1B28 engines with over 29,000 lbs of thrust).

Pushing a significantly heavier airplane into the air with the same amount of thrust requires a bit more pavement to do so. Assuming MTOW is increased to 165,000 lbs, we can estimate the runway required to get an A220-500 at maximum weight into the air. We also have access to the A220-300 take-off runway required charts, which show the runway length required based on outside temperature and the elevation of the airport.

(Author’s note: You also have access to these performance charts. They are available in the publicly published airport planning documents.

You should probably also be aware of how airport elevation and temperature affect aircraft performance. In a vastly oversimplified nutshell, airplanes push air backward to move forward. In dense air, more air is available to push backward, increasing acceleration among other good things. Air is denser at lower elevations and colder temperatures. Air is less dense at higher elevations and higher temperatures. Long story short, it’s really easy to take off from London in the winter, but a real pain in the butt to get off the ground in Denver in the summer.)

The A220-500 will be very sensitive to elevation and temperature. The above chart assumes summer temperatures (ISA +15), which is certainly more challenging, but it turns out airlines like to operate their aircraft throughout the year, especially the peak summer months.

Our extrapolated estimate is that a simply stretched A220-500 will be able to operate at max take-off weight at about 48% of the world’s airports during the summer. That’s not great.

But, this assumes the PW1500G sees no thrust bump similar to what the PW1100G received for the A321XLR. While the architecture and fan are certainly limited, Pratt & Whitney is improving the engines, and it is logical to expect a thrust bump for the A220-500 on the order of about 5%-6%. We are literally making this up as we go, but we’ll call it the PW1526G for grins. Still counts as a “simple stretch,” just slightly less simple.

By our estimates, this will open another 13% of airfields to the A220-500 at max weight in the summer. Final tally, the A220-500 will be able to operate at max take-off weight at about 61% of the world’s airports with commercial service.

This does not mean the aircraft will not be able to depart at all from airports in the red; it will need to reduce weight to do so. That means either fuel or passengers.

For instance, based on our rough estimates, summer range for a fully loaded max-density A220-500 out of LGA without a thrust bump will be about… 1,200 nautical miles. Not great, but it’s not as bad as it sounds. In a more typical 150-passenger configuration, full passenger summer range out of LGA is more likely to be closer to 1,800 nautical miles.

Again, while that appears to pale in comparison to the 3,800 nm range published for the 737-8, it is certainly workable, especially for an airline such as Delta Air Lines. Last summer, Delta operated no flights out of LGA beyond 1,403 nm.

But for comparison, let’s consider how the 737-8 compares at the same passenger loads as the A220-500 example.

See the difference?

And this is why the A220-500 is no real threat to the 737-8. It’s a different type of airplane.

While the A220-500 will be able to serve its hypothetical 165,000 lb MTOW from 61.0% of airports in the summer, the 737-8 will be able to serve the same payload (plus its extra structural weight) at 98.6% of all commercial airports in the summer.

The 737-8 is roughly 10 seats larger in all configurations, can carry more people further from shorter runways - oh, and it has a massive production and commonality advantage.

It will be just fine.

What about the A320neo? Same story, just without the 10 seats.

Frankly, that depends on what you call “successful.” Could the A220-500 sell sufficiently to fill out a 14-aircraft-per-month production line? Yes, absolutely. Could it fill out a 62-aircraft-per-month line? No.

And this resets the expectation for what an A220-500 could be. It is likely to be the second-best seller of the A220 family, but it will not come close to rivaling the 737 or A320. For many, that will not look like a success.

Consider the perspective of the world’s largest lessor, AerCap. CEO Aengus Kelly was recently quoted in an Aviation Week article saying, “Candidly, I just don’t see anywhere in the market that the airplane is needed.”

In fairness, this is exactly what you would expect a lessor to say: “Don’t build anything better because we want the stuff we already have to be worth more.” But the A220-500 will deliver in smaller numbers than the A320neo and 737-8, likely too small for the likes of AerCap to consider - (until Delta asks for a lease, of course. Then it’s all roses.)

For airlines, the aircraft makes sense. Delta is the obvious choice, but there are examples around the world where reduced seat costs are preferred, elevations are low, and runways are long. The usual suspects top the list.

But there are many places this aircraft will not find access due to its addiction to long strips of pavement in thick air. Airfields in much of Latin America and Africa are too high, too hot, too short, or a combination of all three. The Middle East and India become challenging for similar reasons.

And there are other challenges Airbus Canada will need to overcome to deliver the hypothetical airplane we assumed here. Landing gear and structural issues in dealing with the heavier weights will need to be resolved. Larger environmental systems could further add weight. A flight test program still needs to be conducted (and paid for). Simple stretches aren’t exactly simple; they’re just not as complex. But these are all reasonable challenges, and in the grand context of aircraft design, they are quite simple.

In the end, we tend to think of the A220-500 as similar to the 737-900ER. A seat cost machine that traded airfield performance for economics. Probably not successful by AerCap’s standards, but it certainly was for Boeing and for the airlines that use it.

If airlines are interested, the program will proceed, and we expect it to be successful by the judges that matter: Airbus and the airlines.

Remember our nugget of truth theory last week regarding the unsubstantiated Frontier bankruptcy rumors?

The airline announced this week that it will be returning 24 A320neos to AerCap early. That’s a big deal, and certainly something that could fuel the rumors flooding the markets over the past two weeks.

We still don’t rely on rumors, and the most you’re likely to hear from us revolves around whether the data substantiates the rumors being spread. The bankruptcy rumor just didn’t make sense.

But the rumor to return LEAP-powered A320neos to AerCap early certainly did make sense. We just don’t share it with you until it’s no longer a rumor.

But why does the number 24 matter? It doesn’t. But the number 48 does.

We expect the 24 airplanes to be converted into 48 engines. Even though the world is still in a narrowbody shortage (for now), it’s the engines it really needs. If we were AerCap, we’d be happy to take the airplanes back early if they had fresh engines that could be leased out to the desperate airlines separately - and probably for more of those sweet, sweet dollars.

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