Gajre539

I was training a multi-commercial student yesterday, and requested "High speed taxi down Runway 27" to show my student engine failure procedures during the take-off roll (performed at or below 50% of VMC).

Tower responded back with, "Cleared for the option 27". We both look at each other, and not knowing what to say to that, I respond with "Roger, cleared option 27".

I look up Section 8. Spacing and Sequencing, 3-8-1. SEQUENCE/SPACING APPLICATION on ATC Order JO 7110.65T, which states what I already know... "The “Cleared for the Option” procedure will permit an instructor pilot/flight examiner/pilot the option to make a touch-and-go, low approach, missed approach, stop- and-go, or full stop landing. This procedure will only be used at those locations with an operational control tower and will be subject to ATC approval."

What were my options, since I can't take off without a take-off clearance? Possibly a confused controller or a trainee? Anyone get this before?

galaxy flyer

I don't think the controller understood your request because one of the "options" is NOT high speed taxi operations. BTW, you might consider VmcG, next time.

GF

NoyGonnaDoIt

It may not be controller handbook verbiage but I have heard "cleared for the option" on takeoff in exactly the situation in the original post - engine-out demonstrations on takeoff. I've even heard of it asked for that way.

rickair7777

What they mean is that you are cleared for takeoff, b ut have the option of aborting for training purposes.

They do it this way so you can keep the student guessing...he doesn't know for sure if you're going to cut an engine.

Gajre539

That makes sense, thanks rickair7777.

Re: VmcG - The twin that I fly does not have a listed VmcG speed in the POH or AFM. Vr and Vmc are listed at 80 MPH, Vlof is 85 MPH and Vyse is 105 MPH. The PTSs state that engine-outs on the ground should be done at 50% of VMC. "ENGINE FAILURE DURING TAKEOFF BEFORE VMC (SIMULATED-AMEL and AMES) - NOTE: Engine failure (simulated) shall be accomplished before reaching 50 percent of the VMC”. I understand the definition of VmcA, but the PTS does not specify VmcA or VmcG. Doesn't VmcG only apply to transport category airplanes? If it applies to light twins, anyone have a formula to calculate it?

galaxy flyer

The physics of Vmcg apply to multi-engine aircraft, the regulatory requirement is for FAR 25 Transport Category aircraft. BUT, you don't know the Vmcg, so don't get too far into the take-off roll and "pull"an engine and find out their is not enough rudder to hold it straight, but the speed is such you are nearing the edge unexpectedly fast.

GF

NoyGonnaDoIt

One would hope than an instructor using this training method already knows from experience how the airplane will react.

sqwkvfr

Huh?

The physics of an engine failure on the takeoff roll would dictate the the further into the takeoff roll, the easier it would be to control the aircraft in the event of loss of power on one engine.

Did I misunderstand your post?

TonyWilliams

Well.... I can say that I never used this phraseology in my ATC tower days at a busy general aviation airport in southern California.

But, of course, "Runway 27, cleared for takeoff" accomplishes exactly the same thing. Yes, you can abort a takeoff, but logic must prevail. If there's a Gulfstream 550 on a 2 mile final, probably a bad plan. I would probably call the tower ahead of time and request aborted take-offs, so they had a heads up.

Cleared for the option is not appropriate. If I had a trainee in the tower doing that, we'd talk about it, and they wouldn't have anything to defend themselves with.

galaxy flyer

Sqwkvfr

Do you understand Vmcg? Yes, as a plane accelerates, the rudder becomes more effective, but there is a speed, below which the rudder cannot overcome the yaw produced by the inoperative or idled engine. Approaching Vmcg, just a few knots one way or the other makes a huge difference in controllability and if the engine isn't very promptly idled will readily send a plane into the dirt. Crosswind also has a significant effect on the actual Vmcg.

In FAR 25 rules, there is a 30 foot deviation from centerline allowed. I can easily see an eager abort training situation on a typical 75 foot wide GA airport near the plane's Vmcg going badly. That's why I bring it up--FAR 23 are not tested for Vmcg speed or characteristics, so you're a test pilot at some point in the take-off.

As Tony said, one of the options in "cleared for the option" is NOT an aborted take-off.

GF