Is a Rotor Tach must Have ?

[Gyro jeff]

If I do math can use engine rpm for rotor spin up is it needed past that ?

 

[Abid]

Get a darn rotor tach and be done with it

 

[Sv.grainne]

Agree, no way to really know what the rotor is doing. I initially run up to 120rrpm, stick back, continue to 150rrpm the start roll, as rrpm increases as I accelerate I know I'm good to go.

 

[MikeBoyette]

It is a must when learning how to prerotate and doing high speed taxi practice. I too felt it was nice to have and doubted I ever looked at it during flight. Boy I was wrong. I flew one machine without one and I found I kept searching for it and it bothered me not knowing exactly what the blades were doing.

 

[ultracruiser41]

Learning proper rotor management and a rotor tach is not necessary. I know alot of people who have flapped rotors with their rotor tachs functioning properly.
None of the machines I’ve built have a rotor tach….. the Cavalon does but it came that way

I believe teaching proper rotor management is essential in keeping your rotors from getting bent

But….. more information for the pilot is always good….. but useless if not used or the how and why a rotor works is not completely understood.

Fly safe my friends

 

[GyrOZprey]

I have seen a CFI flap rotors & do lots of damage ...all for lack of rotor tach to double-check ..when a crosswind gust lifted his advancing blade AND nose wheel came up ...which he erroneously thought was the signal his rotors were ready to fly - he gunned the power & all hell broke loose! We the observers could SEE the rotor was just NOT READY!!!

I LOOK UP at my rotor during pre-spin and say there is 100 ,there is 150 ...(and cross -check with tach ...so I KNOW the "blade-blurr" visual )- at different Rrpm ...so if ever my tach is inoperable - I have a sight picture of what it looks like - ready to roll!

 

[Aerofoam]

If you can hear the rotor during acceleration, 10 beats per second is 300rpm.
Generally I have observed the blades start making the distinctive thumping noise when they are about ready to start flying, which for most machines is over 300rpms...
That being said, it is a secondary confirmation, many people are using bicycle tachs on the rotors, quick and dirty....

 

[Resasi]

I do use rotor blur, an the noise as indicators of safe rotor rpm to avoid flap, however I also felt that it wouldn't hurt to ad these in a quite prominent fashion on my EFIS screen that is used for Take Off.

( There are several screens I can quickly rotate through with a knob on the right, according to the phase of flight I am in. For example on engine start up the screen I have I only have engine instruments and no flight instruments since my primary concern at this time in engine monitoring.)

As you can see on the screen dedicated for Take Off, the engine and rotor RPM's are quite prominent as with a quick glance I can see what is happening with them.



On the left my airspeed tape and on the right my altitude are also quite large and in line with the rotor and engine tachs so with a quick glance I have all the priority information in one sweep. My HSI however is quite small as I am in good shape simply looking ahead.

On the bottom row my engine instruments are still quite large and any problems on any one of them the green would go to yellow (caution range...or to red indicating an emergency).

The screen has been set up to give priority information at a glance.

As you advance your power and begin pre-rotation with your brakes on, you can see how as rotor rpm begins to increase your engine RPM will initially decrease...so you will nee to add a bit more power, then as your rotor rpm gets over 160rpm, (in my case), I will bring my stick back, release my brakes and smoothly bring in the power and watch to see a more rapid rise in the rotor rpm.

As I accelerate forward, I then as the nose wheel rises, ease forward on the stick to maintain a wheel balanced position and hold it there an at around 37Kts airspeed Blue lifts off, I then ease forward some more on the stick to hold my altitude just clear of the runway in ground effect and build the airspeed to my chosen climb speed, then hold that.

Once safely off and climbing I can then do my after take off checks, and switch to my flight screen.

I do realise that can do all l this is with the benefit of EFIS, but post this simply to indicate how important I feel the various instruments are at different stages of flight...and that on take off, rotor rpm is a very important piece of knowledge you MUST have.

 

[MilesW]

If I do math can use engine rpm for rotor spin up is it needed past that ?

Thread question - " Is a Rotor Tach must Have ? "

No.

 

[MilesW]

I have seen a CFI flap rotors & do lots of damage ...all for lack of rotor tach to double-check ..when a crosswind gust lifted his advancing blade AND nose wheel came up ...which he erroneously thought was the signal his rotors were ready to fly - he gunned the power & all hell broke loose! We the observers could SEE the rotor was just NOT READY!!!

It wasn't for the lack of a rotor tach

 

[Gyro-nut]

IMO, is it necessary, No. Would I be comfortable without a back up to the visual, probably not.
Do I like KNOWING my rotor is above 100 before stick back and above 200 before adding full power... absolutely. Nor do I want to feel that first bump indicating a flap and hope my reaction time is quick enough to avoid an incident at my advanced age

That said, these aren't supposed to be rocket ships and at my airport with a 5000 ft runway, I'd never 'need' a rotor tach to ensure a smooth, safe increase in RRPM as I slowly add power down the runway.

But why would you build a machine without one; Abid is spot on.

 

[GyroChuck]

Jeff, If you are looking to save some money. This is from a previous post. A few of our club members have used this in the past.

Date: September 30, 1999 08:27 AM

Author: Mike Schulman ([email protected])

Subject: $15 (or less) Rotor Tach

I've had several people ask me about this so I decided to post it. This rotor tach is cheap, dependable and accurate. There are several places that you can get this tach. I got mine at Wal-Mart but you can also get it at Target, K-Mart and a lot of bicycle shops. It is the 5 function Cyclocomputer made by ACE Model # 810-230. It is sold under various brands but it is always identified by the Model #. It is powered by a small battery (with auto on-off) The directions are very simple and easy to set. It comes with about 6' of cable and you will need to splice in a longer section - I have lengthened my cable to 10 ' and it still works. You mount the magnet to the prerotator ring or to the rotor head, and then you mount the pickup where the magnet will pass within 1/4" of it. Read the instruction for setting the cyclometer and set it for metric "L" with the number 1667. (If you prefer to use two magnets, space them 180 deg apart and set it with the number 833). Mount the digital readout where it is convenient --and there you have it!! The read out will show a decimal point right before the last digit-just disregard it. The unit is accurate to within five (5) RPM. (BTW this is not my idea Tom Sled told me about it!!)

Mike

 

[GyrOZprey]

It wasn't for the lack of a rotor tach

NO ...that is also true! BUT the information FROM A ROTOR TACH - IF cross-checked would have been good information - that an ABNORMAL situation was happening!

When asked after the horrible demo -of how NOT to do a gyro TO ..resulting in the sickening sounds of chopped parts & flying pieces - "Didn't you check your rotor Rrpm tach BEFORE adding full power" ??? ...he admitted he did not have one and never used one! He got fooled by the gust of wind lifting his nose wheel ...which was the usual indicator that the rotor was ready to fly & and at a safe speed to add full power!

A classic eg of CCC ( crowds, cameras,confidence) - & screw-up!

 

[nevcam]

Thread question - " Is a Rotor Tach must Have ? "

No.

It's a nice to have, but for those people who stir their coffee with their thumb it's a waste, like a teaspoon. More knowledge cannot hurt.