3 Interesting Interview Questions...

[j328ernest]

Received some interesting practice interview questions recently:

1. A contaminated runways affects which speeds? I think it's V1, Vr, and V2. Am I correct and complete? (Someone else said Vy but I can't figure why.)

2. When does an instrument approach turn into an 'Alpha' approach? I thought it was when the final approach SEGMENT course versus the applicable runway centerline headline differed more than 30 degrees from each each other, thus requiring it to be a circling approach. Am I correct?

3. Under IFR rules what are the lowest takeoff WX mins under Part 91? I though unless the departure point had an IAP with either applicable takeoff WX mins or published straight-in landing WX mins there are none - in other words either none OR (on a guess, entering Class G airspace it would be 1 mile) Am I correct?

 

[WMUSIGPI]

#1 I believe only V1 and Vr are affected (not positive)

#2 when the approach course is over 30 degrees from the runway OR if the minimums are too high to make a normal descent to landing without circling.

#3 There are no listed takeoff minimums for part 91. If you are comfortable taking off, enjoy.

 

[JB74]

I have a question about #3.

When does the "two engines or less - 1sm; more than two engines - 1/2sm" rule apply under part 91?

 

[DAS at 10/250]

When does the "two engines or less - 1sm; more than two engines - 1/2sm" rule apply under part 91?

It doesn't.

 

[labbats]

Ya. Part 91 falls under "legal but not smart" a lot.

 

[av8orboy]

Here is a good ? I had..

"Tell me ten things you can bring to the company?"

Come on...

 

[pilotman2105]

LOL. That's horendous to ask during an interview.

I'm in the middle of conducting interviews for a position that I'm leaving in May (basically I gotta hire my replacement). I would never think about asking something like that. Yeah, we ask something along the lines of "What do you think could be done better at our company?" or "What concerns you about the position?" but not "TEN things!"

I'd buy you a beer for havin' to go through that one.

 

[CaSyndrm]

V2 is a inflight speed and isn't affected by a contaminated runway. Most of the rest was correct.

 

[pilotyip]

Part 91 TO mins

If no other minimums are published, then standard mins apply. A 91 operator may take off 0/0. If there are published TO mins for that RW, then the operator must comply with the published minimums. For example RW 27 FNT no published mins TO 0/0 would be legal (note legal, maybe not smart), RW 9 FNT published 300-1, you must have 300' and one mile to take off on RW 9.

 

[ROB-x38]

G'day

With a contaminated runway I presume you would reduce V1 due to reduced braking effectiveness. So given that there is no problem with the obvious requirement that V1 must be less than or equal to Vr, I was wondering why Vr changes? Isn't rotate speed really just dependent on flap setting and aircraft weight?

Cheers

Rob.

 

[A Squared]

Re: Part 91 TO mins

If there are published TO mins for that RW, then the operator must comply with the published minimums. For example RW 27 FNT no published mins TO 0/0 would be legal (note legal, maybe not smart), RW 9 FNT published 300-1, you must have 300' and one mile to take off on RW 9.

Pilotyip,

that is not correct. There is no requirment for a part 91 operator to abide by *any* takeoff minimum. Read 91.175(f) carefully. I've copied it below for reference.

Notice that if you are flying under 121,125,129 or 135, you are forbidden to take off unless the Wx conditions "are at or above the weather minimum for IFR takeoff prescribed for that airport under part 97 of this chapter. "

When they say "prescribed for that airport under Part 97 of this chapter" they are referring to the takeoff minimums printed on the approach plate. If takeoff minimums are not prescibed then the pilot flying under 121, 125, 129 or 135 must use the standard takeoff minimums.

Now here's the relevant point, go back and read carefully, Nowhere does it address pilots who *aren't* operating under part 121,125,129 or 135. The regulation imposes no requirement at all on pilots who aren't flying under those parts. Takeoff minimums are not mentiond elsewhere in Part 91


91.175 (f) Civil airport takeoff minimums. Unless otherwise authorized by the Administrator, no pilot operating an aircraft under parts 121, 125, 129, or 135 of this chapter may take off from a civil airport under IFR unless weather conditions are at or above the weather minimum for IFR takeoff prescribed for that airport under part 97 of this chapter. If takeoff minimums are not prescribed under part 97 of this chapter for a particular airport, the following minimums apply to takeoffs under IFR for aircraft operating under those parts:

(1) For aircraft, other than helicopters, having two engines or less -- 1 statute mile visibility.

(2) For aircraft having more than two engines -- 1/2 statute mile visibility.

(3) For helicopters -- 1/2 statute mile visibility.

 

[pilotyip]

A2 You may be right

I am only going by what a FED told me during an oral many years ago when I was going for a type rating. Anyone else care to comment? AVBUG where are you when we need you?

 

[ROB-x38]

Surely someone knows the answer to my question above???

And one more for anyone game: given that Vr is designed so that the aircraft reaches V2 at 35', would changing Vr then also change V2, so that the answer to question (1) couldn't be V1 and Vr alone?? Anyone?

 

[avbug]

Reducing V1 is a yuppie mind game. It might fit theoretical numbers for acquiring a stopping distance within the conaminated runway's available space (runway plus any clearway or stopway)...but doesn't make you any safer. If you predicate establishment of V1 upon a takeoff safety decision speed, you imply that any failures after V1 require acceleration to a safe rotation and takeoff speed. This will yet require more distance on a contaminated runway; you're still going to need the room. Lose an engine at a reduced V1 and try to accelerate, you're going to require more room; your accelerate-go distance increases.

Unbalancing the field to crunch numbers makes people happy; you can stop, great. You just can't go safely, and going is much safer than stoping in most cases...especially on a contaminated runway.

Theoretical world says dropping V1 is great; tells you when you can get stopped. Real world says big deal...this is where the rubber meets the runway. Where you really do need to be able to continue after that imaginary reduced V1. If you find that you can't get stopped during takeoff on a contaminated runway using a dry-runway V1, then reduce weight, or choose a different runway. Be realistic.

Not theoretical.

Remember also that Vmcg increases with a contaminated runway. Minimum ground control speed is predicated on dry runway conditions and dry tire friction coefficients. Assymetrical thrust conditions on a contaminated runway, contrasted against a lowered ability of the tire to resist (remember, Vmcg is a combination of aerodynamic control and tire coefficient) lateral displacement means that you have a higher ground minimum control speed. Lowering V1 to any point below this is fruitless...you cannot (or should not attempt to) continue the takeoff with directional issues from a speed below Vmcg.

If you do reduce V1 to a lesser speed than Vmcg, you must reduce power on an operating opposite engine to maintain controllability if attempting to continue the takeoff after a failure above the reduced V1 but below Vmcg, thus increasing ground takeoff distance even further.

Using reduced V1 is a cute mind game, but doesn't change the real world one iota in your favor; it only increases the distance you'll need to go in the event you do experience an engine failure at or above the reduced V1.

With respect to Vr and V2, these are weight-predicated, and aerodynamic issues. You don't want to be rotating at lesser speeds, and V2 is nothing more than a speed to meet second segment climb requirements. There is no valid reason to consider decreasing either one for a contaminated runway.

With respect to takeoff minimums, A Squared is correct that pilots operating under Part 91 may depart with less than minimums published under Part 97. No minimums exist for pilots operating under Part 91, though I believe ignorance of published minimums is unwise, despite the regulation under which a pilot may operate.