How does a starter on an airplane work? It's for a children's book I'm writing.

Hello,

I'm writing a children's book about a young girl who's a computer whiz geared for ages 0 to 8. She's getting ready to take a trip on an airplane but they airplane is broken. She uses her computer skills to communicate with the airplane's system to help diagnose the problem. She discovers that something is wrong with the starter. I have this line:

“Well”, said Monique hovering over her computer. “It looks like the starter in Airplane Andy’s engine is broken.” A starter communicates with the motor of the airplane so the engine can run.

Is this technically correct? Does a starter communicate with the motor so the engine can run? If not what does a starter do and how would you explain it to a 5 year old?

Wow.

This is kinda a toughie. Depending on the kind of plane, jet, turboprop, or propeller, the starters are all different. And on jets and turboprops, there are two main different types.

On a propeller airplane, the starter is an electric motor that makes hte engine turn round and round, until it starts firing the fuel/air mixture in the cylanders with the sparkplugs. Does it "communicate" with the engine to make it work? I guess, if by communicate you mean it makes the engine go round. Like your car. When you turn the key, an electric motor run off the car's battery makes the engine go round and round, etc etc.

Jets and turboprops, which is a propeller turned by a jet engine, not an internal combustion (car-type) engine, so needs a slightly different starter set-up. Jet engines are somewhat unique. They suck air in the front, squeeze it to a higher pressure, it then flows into "burner cans" where fuel is mixed with it and burns, and then it flows out the back, on the way making a turbine turn round and round, because when the fuel is added and burns it makes the air very hot and thus it has a lot of energy in it, so it can make the turbine rotate, which is on a shaft that turns the compresser blades to squeeeeze the air.

Just remember "Suck, Squeeze, bang, blow" That's how a jet works.

To make it start, you can either have an electric motor turn the one shaft that has the compesser blades (the SQUEEZE part) and the turbine blades (the BLOW part), until the air is squeezed enough, and moving fast enough, to burn in the burner cans, thus making the engine begin to work on it's own.

Another way to start a jet/turboprop engine is to blow air into a small "starter motor", which is like blowing on a fan really hard. YOU make the fan turn on it's shaft, not the other way around. Works the same with a jet/turboprop. Blow air really hard on the starter motor, it turns the shaft of the engine which has the squeeze and blow blades mounted on it...etc etc.

SO: does a starter "communicate" with engine? No. It makes the engine turn, more slowly than when it runs, but fast enough to make it run on it's own. Like turning a crank to make a toy go around, or the way the electric motor on a fan makes the blades turn, but it all happens a lot faster...

Is all that about as clear as mud?

Pat☺

how would you explain it to a 5 year old?

All starters basically do the same thing, they get the engine 'spinning'

The starter has to have energy (electricity) to work

Explain to the kids that the starter just isn't getting enough energy

They'll get it

You didn't mention what type of airplane. Just saying airplane is like saying "ground vehicle." Is it a car, a truck, a motorcycle, bus, train or what? Airplanes have a similar variety of types, and the type, in general, affects how the start sequence works, generally more complex on a jet than on a propeller airplane. However in both the starter is an electric motor connected to the airplane's engine, though that's often where the similarity stops. (I'm disregarding certain specialized types that use compressed air and other unusual means for starting).

"Airplane Andy" makes it sound (to me) like a light single or twin engine airplane, not a jet. Is that what you have in mind?

Is this technically correct? Does a starter communicate with the motor so the engine can run? If not what does a starter do and how would you explain it to a 5 year old?

No, not in the computer sense, if you're talking about a typical light propeller driven airplane. The starter itself is just like a car's starter, and computer skills wouldn't have anything to do with troubleshooting it.

As Pat says, it's just an electric motor that turns the engine over, just like on a car.

And unlike cars of today, there's not a computer involved in the fuel or spark operations, either -- much simpler than today's cars, much more like cars of the '60s and before, with spark and fuel control done mechanically.

If the airplane is a modern jet, there's much more room for computers there, in the control of the starter, not the starter itself, but it's not generally material for a 5 year old.

“Well”, said Monique hovering over her computer. “It looks like the starter in Airplane Andy’s engine is broken.”

There's no way a computer will tell you a starter is broken, though in a jet it might find that the computer that controls the start sequence isn't right.

A starter communicates with the motor of the airplane so the engine can run.

The starter doesn't actually "communicate" with the engine, but it's physically attached to the engine. The starter switch applies electricity to the starter making that electric motor run, turning the engine over until it starts.

Disclaimer....

I know little about engines really...

I would make it a defective Starter Switch problem.

By measuring the current in the cable, you can detect that turning the strater switch to the ON position does not send current down the cable. That means no current reaches the starter motor.

There could still be 2 causes:

-1-

No current sent to the starter switch from the battery. (broken cable)

-2-

Or current sent to the starter switch, cable is fine, but making contact with the switch sends no current down the cable to the starter motor.

Meaning broken starter switch.

-------------------------

You can exclude option -2- by taking out the starter switch, and making contact between point A and B directly.

(hotwire the engine).

If that starts the engine, then it was a broken starter switch.

If it does not start it is a broken cable somewhere.

---------------------

Oversimplified drawing of engine:

(starter motor turns driveshaft, which makes the engine start.)

It all depends on the type of airplane... For now, I'm going to assume it is a Cessna (or equal equivalent.) The starter a prop airplane is a unit that delivers electricity to an engine to get it to start turning. Fuel and air are injected into the spinning cylinders, kick starting the suck squeeze bang pop process we all know about.

You could choose to make the fault any number of things, like a faulty starter switch, faulty battery, or even a broken starter itself. I don't know how a "computer whizz" could diagnose a problem that quickly, as it can take a trained airplane mechanic hours to figure out a problem like that. The only circumstance I could think of where a computer junky could diagnose a problem on the fly is with complex airliners that have dedicated computers & screens to display malfunctions and errors.

I'd disagree a little with that drawing -- it's a rare small airplane that has a drive shaft, at least in the sense that a car has, though there is a crankshaft internally within the engine, and the prop is usually mounted directly on that crank, though a few have some gearing first:

https://i.ytimg.com/vi/tjDAjo8CtSU/maxresdefault.jpg

On the front of the engine, near the yellow ring, you can see the prop mounting bolts on the flywheel, mounted on the front extension of the crankshaft. At the bottom of that flywheel you can see the silver front of the starter, resting against the flywheel (well, sorta resting). Although that Cub was made long before computers, most light aircraft today use a similar setup, much like il88pp's drawing, also without computers involved.

Hope all the info posted here helps and is clear enough to understand. If not, feel free to ask for clarification.

Hello,

 

I'm writing a children's book about a young girl who's a computer whiz geared for ages 0 to 8. She's getting ready to take a trip on an airplane but they airplane is broken. She uses her computer skills to communicate with the airplane's system to help diagnose the problem. She discovers that something is wrong with the starter. I have this line:

 

“Well”, said Monique hovering over her computer. “It looks like the starter in Airplane Andy’s engine is broken.” A starter communicates with the motor of the airplane so the engine can run.

 

Is this technically correct? Does a starter communicate with the motor so the engine can run? If not what does a starter do and how would you explain it to a 5 year old?

I don't know what these guys are talking about. It seems to work by communication after I scream "Clear!" [emoji23][emoji23][emoji23]

Hi Dave,

LOL - I bet all the other jet jockeys make fun of you with your head sticking out the ERJ when doing it...

:)

Regards,

Scott

Sent from my iPhone using Tapatalk

Ah, did anyone notice that tsims25 added (Thread #5) that it was a commercial airliner they had in mind?

I'm not familiar with starting jet engines, but it does involve starting a motor to rotate the turbofans, and then the ignition of jet fuel, causing combustion. What could go wrong in the failure to start one or more jet engines is, well, a question for all the RW aircraft mechanics out there, not me...

A lot more issues than these:

if it is a recip, are the magnetos ON? is there fuel in the plane? Does the engine require boost pump pressure to start and or run?

If a jet, are boosts on if necessary? Are the fuel cutoff levers actually firing the igniters for lightoff?

Lots of different types, lots of different problems!

In many tactical jets, there is no GPU and the starter is not an electric motor, but an air impingement turbine powered by a ground air source, as well as an electical cart because there is often no battery (an emergency Ram Air Turbine - a "RAT" - is used in an emergency in flight). This all saves weight and complexity.

Thanks for all the great advice! I should have specified what type of plane. I'm talking about a commercial airliner.

Depends on the jet. Majority the starters are electronically actuated to open air valves of pressurized air to turn an impeller which then turns a gearbox which turns the core shaft of compressor blades. However the device that does all of this coordination of valves opening and closing is done by a full authority digital electronic control unit. FADEC for short. There are typically two per engine for redundancy and they actually communicate with each other (engine to engine and also between the current controlling and redundant unit).

To (I guess) answer your question, I don't know of a jet where a starter communicates with the engine itself. However, for a kids book, I don't think it has to be 100% portrayed in the real world. I'd be happy the way it is so kids know that a starter is what starts an engine, whether it be an electric motor or air turbine motor.

A jet engine is a fundamentally simple device - it turns rotation into explosion, and explosion into rotation. And out of that comes thrust.

To avoid the chicken and egg conversation, all jey engines start the same way - a device (could be a motor, could be air, could be a separate starter on a cart on the ground) spins the fan to a predetermined rotation. Fuel is then introduced and some form of ignition is used to begin what is then a self-perpetuating process - the ignition causes rotation, the rotation induces the pressurising of the fuel and air, whcih is then ignited yo cause mre rotation - so the principle is simple - the starter is only used to begin the process. Metering of the fuel is used to control thrust - and if you cut the fuel, you kill ignition.

For a childrens book I'd eschew explanations about `starters` - your whiz-kid can use her computer to deduce that the fuel is not being introduced correctly, and through her superior skills, fix it.