07 March 2010

Big Numbers and The Problem of Understanding.

The engines were crap.
It was 1990 and I had just started flying the BK117.
It had two Lycoming LTS101 engines. The manufacturer of the aircraft actually printed a piece of propaganda showing how two engines are safer than one...
The problem with that was that there was another statistic known by most helicopter pilots...
The Bell 206 series... the Bell JetRanger/LongRanger, was statistically the safest aircraft flying.
Not the safest helicopter flying...
Per hour flown, the safest AIRCRAFT flying. And it had only ONE engine.

It's hard to tout the "twin engine safety" of the machine you're selling when the engines are literally "exploding" with frequent regularity. Those of us flying BK117's had heard the news of the beautiful
Bell 222, the same machine that was used in the television series "Airwolf", that had one Lycoming LTS101 disintegrate, sending debris through the engine compartment at a high enough velocity to destroy the Lycoming on the other side...
And when was an engine most likely to quit producing power?
When you were demanding it produce as much power as it possibly could... out of a tight Landing Zone, for instance. And like a twin-engine airplane, there is a speed at which the helicopter can fly on one engine... a little over 50 knots for the BK117. If one gave out below that speed the helicopter was coming back to the ground. So it was important to pick your place to have an emergency carefully.
"Twin-Engine Safety"? With these engines, that was sort of a cruel joke.

We had two of these machines. For a time, they were co-located because management felt centralizing them would mean cost-savings if mechanics didn't have to drive long distances to maintain them. The pilot working the same shift as me was an interesting character...
He was a Juris Doctor. He had gone to law school, passed the bar, and started practicing law.
He hated the job. Hated it so much he volunteered to become an ARMY helicopter pilot at the height of the Viet Nam war. Returning from his tour in Viet Nam he went back to school and got a Doctorate in history. He was intelligent, engaging, and interesting.

We shared the "Pilot's Quarters" where there were two single beds. One late night we were discussing the "Twin-Engine Safety" issue and "John" mentioned the fact the problem with the BK117 could be resolved by simply replacing the Lycoming engines with a similar Turbomeca engine... that one of these Turbomeca engines had been tested for "one million hours" without a failure.
I was skeptical. "Are you sure of that number, John?"
"Yep. All they'd have to do to fix the problem with the BK is put on Turbomecas."

I got out of bed, turned on the light, and got a calculator.
"Let's see now... 24 X 365 means there are 8,760 hours in a year.
One million hours would equal 114 years. So you're telling me there is a Turbomeca engine that ran for 114 years without a failure? They started running this engine back in the late 1800's?"

A million is a huge number.
A Billion is one thousand million.
A Trillion is one thousand billion.

The Obama administration just added about $10 Trillion in debt to our deficit projections ten years from now. That works out to an additional $30,000 of debt for every man, woman, and child presently in the United States.

My friend the Juris Doctor/History P.H.D. had trouble understanding the number ONE MILLION...
NO ONE can really understand TEN TRILLION.
And that's why our economy is on a runaway train.


Bloviating Zeppelin said...




Bloviating Zeppelin said...

Lycomings were really that bad??


Greybeard said...

The "Lycs" on the Huey and Chinook were VERY reliable, BZ, and that is what confuses many. The company had a reputation for quality and reliability in their recips and early turbines.
Then they designed the LTS101, and the engine was designed with "ease of maintenance" in mind. The engine is modular... most things are easy to get to, and when something goes wrong with a module you simply remove a few bolts and replace it. But the power-turbine wheels were a problem. They were shifting, fatiguing, and disintegrating. Fixing that problem was gonna be expensive. The company merged initially with Bendix-King, then again with Allied-Signal. All the while, they were tinkering with patches rather than actually fixing the $$$$
problem. Finally they bit the bullet, redisigned the entire power turbine section, and the engine is now reliable as a brick, thank God.
In '92 I actually had one explode on me during startup... one of the most stressful times for the engine because you're going from ambient temperature to sometimes 700+ degrees centigrade in a few seconds.
I was mighty glad it did it during starting, rather than when I was desperately needing all the power it could give me!

Bloviating Zeppelin said...

Holy CRAP! Lucky indeed!


RotorSpace said...

We had a PHi BK-117 in my area that suffered engine lost while transporting a patient to a local trauma center, luckily the 2nd engine was able to carry them enough to do an auto at the airport.