Pilots Revving Engines Too Hard Led to IndiGo’s Airbus Woes | Hacker News Reader

Pilots Revving Engines Too Hard Led to IndiGo’s Airbus Woes

bloomberg.com

32 pointsEdwardDiego25 comments

This is very ominous:

"The issue has been costly. The DGCA this week said every time a new plane joins IndiGo’s fleet, it must ground one A320neo that hasn’t had its engines fixed."

You'd hope they would ground them when they need to ground them, not when they can be replaced!

I suspect that's just wording. I bet the author means to say that the two rates are about the same.

It's not. The DGCA is the Indian equivalent of the FAA and "said" means "ordered" in this context.

Further down in the article there is discussion about IndiGo failing to meet the timetable they were originally given, which is probably the reason for ordering them to take planes out of service when they get new ones:

> India originally asked IndiGo to replace all its faulty engines by Jan. 31, but the DGCA said Monday that the airline’s efforts to meet the deadline didn’t “instill enough confidence.” In a meeting with the regulator Monday, IndiGo offered to replace all unmodified engines by January 2021, but the request was denied, one of the people said, adding that the initial deadline remains.

Jeez. Thanks for pointing that out.

The key thing in this article is that the problem involves a new geared engine design. So besides being a engine type, IndiGo had been deliberately stressing it.

Some other aviation "Ooops!" moments:

Mahalo Airlines in Hawaii ended up shutting down after their inexperienced pilots did hot engine starts, each one taking an ATR turboprop airliner out of service.

The AA587 A300 accident over New York was caused by the pilot applying maximum rudder travel until the vertical stabilizer broke off. Apparently one of his instructors taught him to fight the controls.

What's a hot engine start? Do turboprops need to be cool on startup?

I don't know how it is for turbines, but with pistons, an aviation engine is designed very differently from an automotive one, and one of the distinguishing features of the former is that it is designed to run at full load for much of its lifespan. In comparison, an automotive engine spends very little time at full load, even in a racing application. A plane needs a lot of continuous thrust just to keep it moving forward fast enough and generating lift, whereas a car moving at constant speed has to only counteract rolling friction and wind resistance.

Don't most airliners power way down at cruising altitude though?

They power down some, but not much: the thrust of jet engines is significantly lower at typical cruising altitudes (because of reduced air density), so it takes almost as much power to cruise as to climb to altitude.

That is not accurate. The efficiency of turbofans goes up as speed increases. A normal commercial high-bypass turbofan is at its most efficient around 1000 km/h, which is a speed it cannot sustain at lower altitudes due to air resistance over the blades.

Just to add, at cruise, N1, the RPMs of the outermost fan on the jet, will peak over 100 percent, but that isn't a function of fuel consumption.

> The efficiency of turbofans goes up as speed increases.

I didn't say efficiency, I said thrust. Nothing you said contradicts anything I said.

You said that the engine has to burn as much fuel in cruise as it does during takeoff.

I said no such thing. I said the engine power had to be almost as high during cruise as during climb to altitude. Engine power setting is not the same as engine fuel consumption.

When you say not much it's hard to agree or disagree, who knows what much is.

Numbers can be added, about 80% is common for cruise altitude.

The performance equations are not linear. One example another pointed out is that thrust goes up as you go faster, you point out that thrust goes down as density gets lower, it's both.

There tend to be max/min points where the influence from one effect is overtaken by another.

It's all in how you rate your engine. Comparing car engines to aircraft engines is apples to oranges since they are not rated the same way.

An aviation engines leaves a decent amount of power on the table in order to be able to claim near continuous duty cycle . Look at their power outputs. They're abysmal compared to similar displacement automotive engines (for something using 100 octane) by the standards of the time they were designed because they are designed for continuous duty If car engines didn't care so much about max power they'd have a higher duty cycle at max power or conversely if aircraft engines cared more about max power it would be easy to make them output greater peak power at which they can't live almost indefinitely.

The heavy equipment section of your local craigslist is littered with stuff powered by boring old automotive engines that are rated at a power output (slightly lower than what they would be rated at in cars/trucks) and given sufficient cooling to run indefinitely at that output.

Revving engines too hard?? Please explain that, I am clueless about flying a plane.

The trick to save fuel in the short-term, ended up costing more in the long terms by means of having to replace engine?

Cheap/short-sighted pilots/IndiGo management or underpowered engine fit by Airbus?

..susceptible to mid-flight shutdowns.. - With the Boeing issue, I am trying to understand if passengers life were endangered? Who is to be blamed for the issue? Pratt & Whitney for making an engine that is not efficient or IndiGo for trying to act smart or Airbus for poorly designing a plane/insufficiently training(ipad training) the pilots?

The U.S. Federal Aviation Administration hasn’t established any connection between the climb procedure and engine problems, she wrote in a text message, adding that the safety of passengers, crew and aircraft remains the utmost priority. - FAA let Boeing kill 2 planes of people and only stopped them after rest of the world grounded the flight. It's not comforting to quote them to assure safety.

The article kind of dances around the issue of attributing blame, but i would be interested to know how this was all arbitrated. Were the engines actually being operated outside of specifications? I presume a manufacturer-approved maintenance schedule was followed by indigo on the planes with in-flight failures, so who is liable? The article makes it sound like the airline is responsible for the replacements, but are they footing 100% of the bill?

I'm intrigued in the age of fly-by-wire that it is possible to rev a jet engine in an unsafe way. I mean machines took control of deceleration of turbines decades ago, didn't they?

The problem is that it's not directly unsafe. It's within the capabilities of the plane, but wasn't intended to be the normal usage.

Same article without a paywall can be found at : https://economictimes.indiatimes.com/industry/transportation...

>IndiGo still needs to replace 110 engines out of 196 that were affected, ...

Essential questions not addressed:

1. What is the nature of the "fix"?

2. Have IndiGo pilots since been directed to limit power to "alt-climb"?

3. What is Pratt's analysis of failure incidence as a function of power history per engine?

It's a geared engine, so gear failure is basically sending the engine back to the factory and rebuilding or discarding it.

This is a big deal, and the reason geared engines haven't been used in aviation turbines before.

If I owned an airline, I wouldn't buy one now or for 2 decades.

Im not too familiar with aviation; what is a geared engine mean in this context, and what does that look like?

https://en.wikipedia.org/wiki/Geared_turbofan

Revving the engine? Sounds 6E.

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