Talking Multi engine

As you may be aware from the Hype train that it’s soon to be B-17 time Zora has pulled out all the stops on this one and there’s a new feature to this plane that is going to be alien to you. It has multiple sources of thrust in the script fully simulating Multi engine flight.


First I need to first address the big grizzly in the room with more engines comes more complexity more dials, switches and gages and more to start up and more to manage. Many Real world private pilots never make that multi engine jump and you’re a SL pilot never touched a true multi engine before in sl and your first jump into multi engines has four of them lucky you! (Well at least you can’t die in Second life)  Scared yet? You shouldn’t be flying the ZSK  B-17 is fun and it will be more so if you keep reading.

Why more than one engine?

You may be asking why would they put pre than one engine on an aircraft or have this odd idea that one is a “spare” this is not the case at all  for example on a twin engine you lose one of those engines you also lose 80 to 90% of your excess thrust. Or in simple terms if you can climb at 1200 Feet per minute with both engines and if you were to lose one and get the aircraft configured to fly perfectly with just the one engine you will only afterwards be able to climb at 200 FPM   in the case of General aviation twins the single engine performance is marginal and very pilot error intolerant and for example a non-turbocharged twin will have a single engine service celling of 5,000 feet density altitude. Meaning on a nice summer day you will not be able to climb at all. And remember the more engines you have the more likely you are to suffer an engine failure!

Than why put more than one engine on a plane ?

Let’s use the B-17 as an example 17 used 4 Pratt & Whitney R-1690 Hornet engines at 525 HP each for a total of 2100 HP a single engine that delivered that power was not available at the cost needed to be charged for the bombers so 4 smaller more economical engines were used to total the needed 2100 HP and for the inconvenience and extra danger of having multiple engines a little extra power was added   (for example 4,  500 HP engines would have been enough)  The sort loose one engine your probably  fine if you are a good pilot but  loose two it is time to think about an emergency landing

The good news is the B-17 Is not scripted for random engine failures you can turn an engine off or if you like VICE combat you can have one shot out. snapshot_007

The big problem is you have 4 engines on your wings and they are all pulling on the aircraft pulling nice and symmetrical but loose one and you face an imbalance the aircraft will want to lean and turn towards the dead engine. It get worse that dead engine and its spinning (wind milling) propeller are creating drag and making the plane yaw further into the dead engine.

In order to save your but you first need to “Feather” the prop or rotate to maximum coarse pitch at this point the propeller of the dead engine will stop rotating.  At this point we need to address the yaw issue as your aircraft slows the controls will get sloppy if you slow down too far you will lose rudder authority and you will not be able to counter the yaw This results in the aircraft rolling inverted into a spin, and nearly always the “deaths” of all the occupants and you don’t want that you want to land that plane. So the first recommended step is to reduce the yaw as much as possible by throttling back your engines on the side where both are still good. Than lower your nose to increase that airspeed.    On the B-17 it is scripted to you can trim for level flight after you take the initial safety measures.

You may be thinking what if I am flying low both of these sound bad! That is why in a multi-engine it is recommended to fly at least twice if not three times that you would in a single engine.  And climbing slowly is very frowned upon in fact so much minimum yaw control speed, known as Vmc, is painted as a red line on the airspeed indicator, in addition to Vne. Rotation on takeoff before Vmc is really discouraged.

At a later date I will go into Weight and balance this was just to serve as a primer for the Multi Engine flight of the B-17 I hope you found it useful

I would like to end with my final thoughts as I had a rather fun seat to watch this aircraft was aircraft devolved.  Over the last six months of its cycle. I have been accused of being a “Fangirl” of one builder or another. I will say it if I were a “Fangirl” of any builder it would be ZSK.  Zora puts a lot of heart into these builds and genuinely wants to deliver the best product possible.
Zora and I had some fantastic talks about multi engine flight and he had a lot of questions on how to make the simulation if multiple engines better. I have only had the chance to fly the B-17 twice once as copilot and once solo and I will say this is as good as it gets in Second life. It is a fantastic product from a fantastic builder.  I hope you consider trying or buying this awesome aircraft.
I wish you many hours of fun in your B-17 !

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4 Responses to Talking Multi engine

  1. stevecavers says:

    This is a nice innovation, in concept (I haven’t tried it). This is exactly the kind of development that should be going on in SL flight — expanding the fundamentals of the flight physics rather than bloating planes with nice-to-have eye candy features.

    I’m tempted to go in-world right now and try using a pair of push forces rather than a single one in the centre of the plane, and see what happens when force is applied off-centre unevenly.

    Even though I’m not 100% certain that it hasn’t been tried before, it’s nice to see stuff like this going on. Nice work!



  2. stevecavers says:

    Reblogged this on Steve Cavers: metaverses, food, and writing and commented:
    Here’s an example of a nice innovation in Second Life flight physics. It’s such a simple idea, yet I can’t think of anyone using this idea in a multi-engine plane. Normally, thrust is applied in a central location and sometimes offset left or right as is needed. In this case, they apply force at the engines, rather than the centre axis, so no offset calculation is needed when engine thrust is imbalanced.


  3. Pingback: SOCL Pilot Hears About ZSK Release, Makes Emergency Landing | Waterbank News

  4. Pingback: Talking Multi Engine – Steve Cavers: metaverses, food, and writing

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