Multi-Engine Instrument Commercial checkride advice


Well-Known Member
I've scheduled my Multi-Add on checkride for next tuesday 9/16/03 and am wondering if anyone has any advice to offer regarding the oral and practical tests. I've found some useful information from older threads on this forum, but am still looking for more gouges. I'll be flying a PA34-200 for the test.

In preperation for the oral, I've been studying the ASA Multi Oral exam guide, going back over the instrument oral exam guide, and studying the seneca POH. Overall, I've got a solid grasp on Aircraft Systems, VMC, Critical engine, and aerodynamic factors affecting single engine flight. Anyone have other "focus" areas I should dig in on for the oral?

The Examiner already told me the location of the single engine approach I'm going to do on the ride (a VOR circle to land). I flew that approach twice today, once with both engines and once single engine so it shouldn't be a problem (I also flew that approach on initial instrument checkride). He'll probably have me do a different type of approach also, but with both engines (ILS or NDB more than likely). The runway at the airport whre I'm meeting the examiner is pretty small, 3204 x 60 ft, but I usually have no problem landing in half that distance using the short field technique. I have no idea how many landings I'll do, probably at least two (one single engine and one short field). The air work doesn't concern me all that much, stalls, VMC demo, and engine air start are all pretty straightforward (as long as I don't verify the dead engine with the wrong throttle!!! hopefully thats one of those mistakes I'll only make once). The steep turns are really not much different from a single so I should be good to go on those.

Did I miss anything? Anyone have troublespots on their checkride that they wish they would've adressed earlier? I've accumulated about 30 hours of dual in the seneca working on this rating over the summer so I feel pretty confident. That's probably more hours than average for an add-on applicant, but the plane was down for two seperate two week periods, necessitating more overall flight time before I attained acceptable profiency. Thanks for the help........
Know your systems, cold. Know Vmc and single engine aerodynamics, cold. And then just go fly. I already had my instrument when I did my Multi-comm (initial) and the ride itself took all of 1.2 in the logbook. It's really rather anti-climatic.
I always go thru the PTS booklet page by page, that usually exactly the way the exam goes. Its a good outline to study from.
Don't forget all that stuff you had to know for private. Sometimes people focus on the 'new' stuff, and forget all the 'old'.
On both my multi checkride and my MEI checkride I was asked about the effects of CG on aircraft handling and performance (stall speed, cruise speed, etc).
Well, I took the checkride today and passed. The flight portion was quite uneventful, consisting of a short field takeoff, Slow Flight, Power on and off stalls, steep turns, VMC demo, Engine shutdown and restart, SE VOR approach, SE circle to land, engine failure during takeoff roll, a Go-Around immediatly followed by an engine failure, and a short field landing. My biggest bluff up was probably rolling out 10-15 degrees late on my second steep turn, but the DE didn't mention it. I also lost about 500 ft (4000 down to 3500) during the engine shutdown, feather, and restart. I didn't want to keep the operating engine at max power, so to save the engine i sacrificed 500 ft. The DE just mentioned that I should "maintain 3500 ft if able" throughout the restart procedure

The oral was a bit more difficult. I nailed the definitions of Critical Engine and Vmc. Then I was asked to explain the conditions under which VMC is determined, so I listed them all. Then he wanted me to categorize each condition as affecting either A) Assymetrical Drag B) Assymetrical Thrust or C) Controlability. The examiner informed me that having the flaps up and gear up should cause VMC to decrease and that 5 degrees of bank into the operating engine and max gross weight should increase VMC. I had read and been taught that the gear and flaps created a "keel effect" when extended, and having them retracted INCREASED VMC. In addition, everything I had read said that being at max gross and 5 degrees of bank DECREASED VMC, but my examiner said that this wasn't true and asked me to explain why it wouldn't be true. I had a lot of trouble with that question, since it went against everything I had been taught, and probably came away from the oral more confused about this subject than I was going in.

One system i didn't expect to be asked much about that the Examiner really focused on was the Janitrol Combustion heater. Specifically he asked me if it had overheat protection. I said no, but told me I was wrong and that it does indeed have overheat protection. He then asked me where the circuit breaker reset for the heater was and I didn't know that either. I've done all my training in the seneca during the Texas summer so operation of the heater hadn't been emphasized, but I wish I would've studied its operation a bit more and maybe turned it on at least once in my training. Basically the only thing I did know about the heater was that you have to leave the fan on after shutdown to allow the heater to cool down, that it draws .5 gallons per hour out of the right fuel tank, that it's located aft of the cabin and is operated by a control panel between the two front seats.

The oral was wrapped up by a brief discussion of the landing gear system. By far we spent the most time discussing the factors under which Vmc is determined and trying to get me to explain "how and why" each factor affects Vmc. My examiner didn't agree at all with the "keel affect" theory or the "5 degrees of bank decreases VMC and max gross weight decreases Vmc" theory. He argued that EVERY factor (Standard day temp & press at Sea level, Flaps Up, Gear Up, Inop Engine Prop Windmilling, Inop engine at zero thrust, Op engine at max thrust, aft legal CG, 5 degrees of bank into operating engine, and Max gross weight) used during Vmc testing INCREASES Vmc because they want Vmc to be the highest number possible. This contradicts several FAA publications but fortunately I managed to wiggle my way through the oral and earn my new rating.
Well, I took the checkride today and passed.

[/ QUOTE ]
OUTSTANDING!!! You and I did the ME thing at the same time (albeit mine wasn't the comm. ride... yet.)

I know this is an old thread but hoping that someone could just help me on my thoughts.

"One system i didn't expect to be asked much about that the Examiner really focused on was the Janitrol Combustion heater."

Just remember when taking a checkride find all the things in the new airplane that all the other ones don't have. That is the most promident questions. Almost like the prop, landing gear when you get in complex, with multi it is vmc, speeds, heater. I have found that to help out a lot on checkrides.

"My examiner didn't agree at all with the "keel affect" theory or the "5 degrees of bank decreases VMC and max gross weight decreases Vmc" theory. He argued that EVERY factor (Standard day temp & press at Sea level, Flaps Up, Gear Up, Inop Engine Prop Windmilling, Inop engine at zero thrust, Op engine at max thrust, aft legal CG, 5 degrees of bank into operating engine, and Max gross weight) used during Vmc testing INCREASES Vmc because they want Vmc to be the highest number possible."

I am currently working on my multi-instr com add on and the way that I understand the whole keel affect is that it does add the keel affect but there is also a lot more drag associated with it, so you may not yaw as much but the drag associated overwhelms the less yaw. So therefore when comparing the amount of lift that you will lose vs less yaw the VMC would increase.

Then with the whole up to 5 degrees and increased weight it also increases VMC because with increased weight requires a higher pitch attitude to sustain level flight, but in a turn it decreases VMC because there is more of a horizontal component of lift. So that is why they limit it to 5 degrees, if you were to continue to bank into your operating engine there would be a point where you would not use rudder at all because the horizontal component of lift would conteract the yaw however you would also have an increase in drag which decreases performance.

I personally believe the examiner just didn't understand what you were saying. But thanks for your info on your checkride, it helps alot to those of us that are coming up on it soon. And for all of you ME and MEI please correct me if I am wrong with those explanations because I want to have the correct information. Those are just the interpretations that I got.

And congrats on the new rating...
I think what tazman is saying, is that without holding 5 degrees of bank into the operating engine, operating at Max Gross with one engine inoperative will increase (or have little effect on) VMC. Being at max gross while ALSO holding 5 degrees of bank does decrease VMC, becuase the wing must produce greater lift to support the plane at max gross than for some other lower weight. Since the total lift is greater, the horizontal component of that lift with 5 degrees of bank will also be greater, therefore decreasing the amount of rudder deflection neeeded to maintain directional control at a given airspeed.

Basically, if you take max gross weight by itself, it doesn't decrease Vmc. It decresases Vmc if, and only if, some degree of bank is held into the operating engine. Just my interpretation.
Hmm well I'm now working on the ME inst /comm add on and this is interesting. I'm getting close to the ride hopefully next week... went through the training pretty quick (6 hrs so far) so I want to make sure I have everything covered.

On the VMC deal at max gross... Even in wings-level flight it will decrease VMC so far as I understand it. My instructor told me if you put 10 pounds on a swivel chair and try to rotate it around with a stick it'll be easy. Put 100 lbs on a chair and it'll be harder. Same thing with VMC and weight which makes sense to me, don't know why your examiner said otherwise.

Also on the gear / flaps deal... the gear would provide the keel effect since most of it is aft of the cg, stabalizing it. On a tailwheel twin it would increase vmc since most is forward of the CG. It's like opening the doors inflight in a 152... it does the opposite of the rudder. Now the drag of the gear loss of performance more than overcomes any stabalizing benefit from having it down.

On flaps it would raise VMC to have them down since the induced airflow would create more lift on the 'good' engine side... and cause an even greater rolling moment.

Anyway that's how I understand this... if anyone has tips and if I'm wrong here please let me know!
Here is a document written by my multi-engine examiner which explains (in his words) all the factors affecting Vmc. It's a pretty interesting read. He emphasizes that EVERY aspect of airplane configuration used in determing Vmc is designed to raise Vmc.

He says the windmilling prop "blocks" the air flowing over the flaps and gear on the side with the failed engine.

However, there is still air hitting the gear on the side of the operating engine. This means there is more drag created on the side with the operating engine than the side with the windmilling prop failed engine. Therefore, having gear and flaps down decreases Vmc.

He argues that operating at maximum gross weight will increase Vmc because of "inertia". When the engine initially fails, the airplane will "swing" around into the failed engine. A heavier mass will swing into the dead engine with more force, thus requireing more rudder pressure to stop than a lighter mass.

And on five degrees of bank:

The pilot of this airplane has banked five degrees in the direction of the operating engine in an attempt to maintain coordinated flight. In order to maintain that bank, the aileron controls must be held in a bank to the right. As pictured the left aileron is deflected downward to increase lift at the left outboard wing, and the right aileron is deflected upward to decrease lift at the right outboard wing. The result is that drag is increased on the left and decreased on the right, increasing the yawing moment to the left. The asymmetrical drag increases the rotational force vector and raises Vmca.

[/ QUOTE ]

I'd encourage you to read the document. It's pretty interesting and seems accurate to me.
Thanks for the link Alchemy... I think I'll just keep it simple for the checkride and stick with what I've learned from other sources; looking forward to getting the cert, checkride is scheduled for a week from Mon.