syncing a 4 propeller airplane

eep...2 Green · Post by **eep...2 Green** » Thu Mar 31, 2005 1:28 am

Those that operate 4 propeller airplanes...tell me a bit about syncrophasing the props please. Maybe it's simpler than I think.

Captain Crunch · Post by **Captain Crunch** » Thu Mar 31, 2005 6:22 am

well, here's the way i would do it, shut down the two inboards (to eliminate noise and adverse yaw as opposed to shutting down one side), then sync 1 and 4, start up 2, sync that, start three and voila, easy as pie... as long as ur not too heavy.

flynbutcher · Post by **flynbutcher** » Thu Mar 31, 2005 7:33 am

Hope you don't do this while you're in cruise.

CLguy · Post by **CLguy** » Thu Mar 31, 2005 8:45 am

They have auto syncronizers!

prang one · Post by **prang one** » Thu Mar 31, 2005 10:04 am

As CL Guy said its auto sync.

But to be more specific. As with a 2 Eng A/C you have a Master and a slave. ( no am not talking about pilot telling copilot to sync those damned props

)

In a 4 engine aircraft its the same (some have a back up master on another engine)
But in essence the Master engine tells all the prop governers on the slave engines what he wants and each engine fine tunes its blade angle to produce the desired result.

It can appear a little complicated as usually the control system is linked into NTS and or Auto feather due to the effect of all 3 revolving around blade angle change.

If you want more specifics PM me. But I am sure you have a manual its just that no amount of mini bar action is helping you understand it.

Juggs · Post by **Juggs** » Thu Mar 31, 2005 10:54 am

This may also be of some use to you.
http://forums.flightinfo.com/showthread.php?t=50096

Cheers,

--Juggs

eep...2 Green · Post by **eep...2 Green** » Thu Mar 31, 2005 2:01 pm

Hey thanks Juggs...

Arrow · Post by **Arrow** » Thu Mar 31, 2005 3:38 pm

If the synchrophase is u/s it is still pretty easy to sync the props. As you are pulling the props back look for a spot in the center between the two props. Here you will find a small strobe effect or shadow. If it moves up or down the props are not synched, and they also sound like crap. When the shadow or strobe does not move, but is stationary the props are in synch. Sounds goofy I know, but it really does work.

bigred · Post by **bigred** » Fri Apr 01, 2005 12:45 am

eep if you are in the hamilton, ottawa or calgary area go to the museums in those areas that have four engine planes that at one time flew and ask the old pilots they are always some around and ask them how they did it.
1. Canadian Warplane Heritage Museum Hamilton Ont
2. National Air Space Museum Ottawa ont
3. Nanton Lancaster Society Museum Nanton Approx 40 miles west of calgary
4. Cant remember the name of it but go to the museum just off the airport in Calgary.

Driving Rain · Post by **Driving Rain** » Fri Apr 01, 2005 5:23 am

Arrow wrote:If the synchrophase is u/s it is still pretty easy to sync the props. As you are pulling the props back look for a spot in the center between the two props. Here you will find a small strobe effect or shadow. If it moves up or down the props are not synched, and they also sound like crap. When the shadow or strobe does not move, but is stationary the props are in synch. Sounds goofy I know, but it really does work.

If the syncrophase is US so is the aircraft. Yes you could sycronize the props and still the wing would depart the aircraft.

Wrench MD · Post by **Wrench MD** » Sat Apr 02, 2005 4:20 pm

Driving Rain wrote:
Arrow wrote:If the synchrophase is u/s it is still pretty easy to sync the props. As you are pulling the props back look for a spot in the center between the two props. Here you will find a small strobe effect or shadow. If it moves up or down the props are not synched, and they also sound like crap. When the shadow or strobe does not move, but is stationary the props are in synch. Sounds goofy I know, but it really does work.
If the syncrophase is US so is the aircraft. Yes you could sycronize the props and still the wing would depart the aircraft.

What? Are you crack? Since when does a syncrophase U/S make the aircraft U/S? (Not taking a MEL into account)
Wheather its 2 props or 4, its not rocket science to sync props, if you know what your doing, you can sync them all manually. Yes it may not be as fine tuned as with sync system operational, but you can still fly and get the job done, safely.

xsbank · Post by **xsbank** » Sat Apr 02, 2005 5:04 pm

Just ask a Dash7 pilot - 4 tiny engines and a synchrophaser that works when its in the mood.

Nice a/c though very slow, not much range and an ice-magnet extraordinaire.

backon3 · Post by **backon3** » Sat Apr 02, 2005 5:47 pm

Man if a u/s synchro meant we couldn't go we wouldn't get off the ground! The shadow method is great and works excellent, only when there is a shadow due to position of aircraft and night time. It's not that hard to sync props on four large radials though, you get an ear for it eventually.

Driving Rain · Post by **Driving Rain** » Mon Apr 04, 2005 7:34 pm

I believe if the "sycrophazer" on the L188 is US so is the aircraft. I saw photo once of the electra wing with the syncrophaser turned off, the wing started to bend as if it was a wave form and was damed near torn off in flight. Early 188 did suffer some catastrophic wing failures because of props out of phase (not the same as out of sync) Sorry, I should have specified that in my original post. I always syncronise by ear. It's the same technic as tuning a musical instrument. Listen for the wa wa wa to blend into one nice wa sound and hold.
It may not be as critical on some aircraft as others. I don't know if the early C130 suffers the same problems as the electra using the same engine and prop combo.

Captain Crunch · Post by **Captain Crunch** » Mon Apr 04, 2005 7:42 pm

flynbutcher wrote: Hope you don't do this while you're in cruise.

I usually do it while climbing out, just to get it out of the way... Sometimes when I am on the ball, I even get it done on the takeoff roll!

xsbank · Post by **xsbank** » Mon Apr 04, 2005 7:57 pm

The reason that Electras shed their wings was due to soft engine mounts and weird harmonics with the rigid wing. The mounts were re-designed and the Electras survived long enough to be eclipsed by the new jets, 707, DC-8 etc.
There used to be a website that had a movie of the flutter effect on an Electra - will see if it is still around. I'll bet a beer that there is NO a/c that will shed its wings if prop sync goes u/s. Besides, lots of large a/c don't have prop sync...like Grumman Trackers/Firecats and DC-3s.

xsbank · Post by **xsbank** » Mon Apr 04, 2005 8:01 pm

Check this out: http://www.airandspacemagazine.com/ASM/ ... utter.html

xsbank · Post by **xsbank** » Mon Apr 04, 2005 8:07 pm

Not to beat this to death, 'reduced stiffness' engine mounts solved the problem.

Lots of other things can kill an Electra too, like flap failure (failed down, run out of gas), or cracked wing planks, or cracked bell frames...

Sync the two on the left with the strobe effect, then do the two on the right, then move two throttles together to eliminate the wa wa. Used to work for me.

DiscoDashSeven · Post by **DiscoDashSeven** » Tue Apr 05, 2005 10:30 am

xsbank wrote:Just ask a Dash7 pilot - 4 tiny engines and a synchrophaser that works when its in the mood.

Nice a/c though very slow, not much range and an ice-magnet extraordinaire.

Tiny?!?!

Ever try lifting one into the back of a Dash 7? Range is only a problem if you want to carry something. We fly it slow cause we need time to think and a little ice builds character.

The syncrophase is on the MEL for the Dash 7.

Kosiw · Post by **Kosiw** » Tue Apr 05, 2005 11:17 am

Dash 7 props can also be "synced" visually if the sun is in the right direction, playing with the prop levers until the shadows in the revolving blades come to a stop.....then bob's your uncle.

As for range, some modified -7's can "technically" hold upwards of 18,000 pnds of fuel, I believe the US army and the CDN ice patrol -7's have this mod, and with the burns down around 1200-1400 lbs/hr at altitude, it can be aloft for a long time, but of course payload suffers greatly.

xsbank · Post by **xsbank** » Tue Apr 05, 2005 3:00 pm

Disco, I loved flying the Dash (4-otter or double-otter) - a real sweety, but definitely best low down (like on and off the ground).

I seem to remember one time shutting off the engines with the sync still engaged and getting a really BAD sound from engine number 2 when next time I turned on the battery master. Called maintenance and after explaining what the sound was and holding the cell out the window, got a real tongue-lashing with parts costs and how difficult it was to fix - you get the picture. Fortunately, all it cost was a red face (mine) and a case of beer (mechanic's) as I turned off the switch.

Picked up a huge load of ice on the BC Coast and fortunately was over water and able to descend; F/A knocked on the door and turning around, you couldn't see out the pax windows at all(!)

Took 9 hours to fly from Thunder Bay to YXX, with 2 stops.

Best and worst trip? Took 40 airline Chief Pilots and Ops. managers on a Boeing charter to the Charlottes to fish - CP from Southwest sat on the jump seat and marvelled at all the little round steam-powered gauges...

syncing a 4 propeller airplane

syncing a 4 propeller airplane

syncing 4 propeller plane