Sport Pilot Talk

flyingeyes · Joined: 09 Aug 2011 Posts: 8

1) One of the LSA planes was getting a fuel leak in the wing repaired and needed to wait 24 hours before putting fuel in that wing. The instructor decided to fill the other side full and do some training with a fairly new student. I'm guessing that is a call the instructor makes. Would that be an appropriate thing to do?

2) If the stall horn is placarded due to malfunction is that something of concern when training a student?

3) Last question, if a student weighs 100 lbs and the POH says a solo pilot must weigh 120 lbs is there any concern when that 100 lb student solos?

Thanks.

bryancobb

flyingeyes wrote: 1) One of the LSA planes was getting a fuel leak in the wing repaired and needed to wait 24 hours before putting fuel in that wing. The instructor decided to fill the other side full and do some training with a fairly new student. I'm guessing that is a call the instructor makes. Would that be an appropriate thing to do?

ANSWER There is nothing wrong, generally, with flying the plane with one empty tank...with a few caveats:
a) Considering instructor and student weights, size of the left and right tanks, and their distance from the CG, is the lateral CG going to remain in a safe location for flight? A heavy wing, requires down aileron to lift the extra weight and that creates induced drag and could be dangerous. Several questions SPECIFIC to THAT aircraft need to be answered by your instructor BEFORE going up with him in that condition. Cary a 50# bag of Play Sand and chunk it in the empty seat.

2) If the stall horn is placarded due to malfunction is that something of concern when training a student?

ANSWER Many aircraft never even had a stall horn. It's a nice feature for a beginning student to be warned 5 knots before stall, but not REQUIRED.

3) Last question, if a student weighs 100 lbs and the POH says a solo pilot must weigh 120 lbs is there any concern when that 100 lb student solos?

ANSWER If the plane NEEDS a 120 pound pilot to avoid an aft CG, then flying without AT LEAST 120 pounds in the cockpit IS DANGEROUS. A airplane with the CG aft of limits is an accident-in-waiting and if you were stall the airplane, EVEN AT ALTITUDE, you may not be able to get it out of the stall.

Thanks.

Jack Tyler · Posted: Sun Aug 28, 2011 5:12 pm Post subject:

My take on your Q's:

1. A judgement call. Some a/c only have a single fuel tank, so flying with a single fuel source is not, by itself, dangerous or even exceptional. Whether it's a reasonable choice may be a different issue depending on the mission.
2. I would not fly without a working stall horn. My bet: The a/c's required equipment list includes a working stall horn. Regardless, IMO it is bad practice generally, and especially bad practice when 'role modeling' pilot behaviors to a student. Surely, they weren't renting that a/c to a student pilot doing solo work?
3. Check that specific a/c's weight & balance documentation (not just a generic W&B or another, sistership's W&B). If your 100# (or 120#...or whatever), along with the fuel load and other items carried aboard for that flight put you outside that a/c's envelope, then you are leaving student pilot status and joining the ranks of test pilots.

Jim Stewart · Joined: 12 Oct 2006 Posts: 259

My airplane doesn't have a stall horn. It's not a problem for me.

As to your situation, the FAR's don't require a stall horn. If you POH doesn't require one, then it's a judgment call.

ibgarrett · Joined: 04 Dec 2008 Posts: 147 Location: Westminster, CO

Hmm - this question sounds oddly familiar to a plane in the flight club I learned with. I'll be happy to give my perspective on it based on the plane I assume this is.

The plane in question is an Evektor SportStar which I did all of my training in. The fuel tank that was being repaired was the left tank, so the recirculation (or reclaimed fuel that drains back into the tanks) of the fuel wasn't being drained into the tank that needed to dry but rather into the tank being used - so no real issue there. The only situation I could see to be at issue would be the plane would be slightly heavier on the right hand side given the additional weight in fuel. The plane I'm currently flying has a single tank in the center of the plane, so there isn't a balance issue there.

There are planes that are made without stall warnings. The StingSport that I currently fly doesn't have one and it isn't on the mandatory equipment list - after all, it shipped from the factory that way. The Evektor in question here does have a stall warning on it and was notorious for going off when there clearly wasn't a stall as well as when you were in a stall. I'm not sure if it was on the list of required equipment, but if the CFI giving the lesson knew of it, I would imagine that information was shared with the student (hopefully - not saying it wasn't)...

On a whim one day, the CFI that typically flies this Evektor and I put in some ridiculous numbers to paper to see if we could get the plane out of W&B. We put a 60lb student solo in the front seat and weighed the cargo area with 20lbs more than the 55lb weight limit (for a total of 75lbs). Oddly enough, the plane was still within the flight envelope. So going lighter than 120lbs student in one seat by 20lbs in this scenario wouldn't be a factor.

Now given the variables involved - the CFI I'm thinking of and the extra fuel being on the right hand side, the plane will certainly be a bit heavier on the right hand side, which would be interesting to fly that way. However given my knowledge and experience with the CFI in question I would trust his judgement. I have never known him to throw caution (or safety) to the wind. I've seen him cancel flights for lesser things because there were other compounding issues effecting the airworthiness of the airplane. I've certainly heard of mistakes that were made, but in my experience with him it was never knowingly done.

But - I could also be a bit defensive about this as I have a soft spot for the Evektor as a reliable and steady aircraft and the CFI is a hard working individual who takes his job (and safety) very seriously. :)

flyingeyes · Joined: 09 Aug 2011 Posts: 8

Brian,

You know exactly where and what I'm talking about. In the example where the right wing was full of fuel and the left wing empty and a gust (ok, just wondering) came up on the right wing on take-off or landing, would that have created a control issue that might be difficult to manage? The CFI did say the flight was "interesting."

When you say the stall horn was notorious for going off before the stall, sounds like a good thing to me. I liked that Evektor stall sound better than Remos anyway.

ibgarrett · Joined: 04 Dec 2008 Posts: 147 Location: Westminster, CO

It probably would have had to have been a pretty strong gust from the left to really make that big of a difference. And if it was a gust enough to make a difference it would've been pretty difficult to control - at least that's only in my opinion. I thought it was interesting that it was being flown that way as well - but what it boils down to, is it do-able? Yup.

I've had the stall warning go off on it while taxiing down the ramp. I've been long-since landed and it continued to go off. I've been in perfectly level flight and it would blip along warning me about something - it certainly wasn't a stall. IMHO a stall warning that continually goes off when there is no stall is worse than no stall warning at all. Because you get conditioned to the stall warning as an indicator that there is an issue that needs to be corrected - but if there is no situation that needs to be corrected, you start to ignore it, and then when you REALLY should be paying attention to it you might be ignoring it.

I agree though - the Remos stall warning indicator is rather annoying. It sounds like interference from a cell phone on the line. The first time I heard it I had no clue that it was even a warning signal.

zaitcev · Joined: 05 Jan 2010 Posts: 258 Location: Albuquerque, NM

There was a Pilatus crash this Spring in Montana or Wyoming somewhere. The pilot neglected to put a required anti-icing additive into fuel and one of the tank's pick-up froze. He took too long to divert, and by the landing time the imbalance was too great for the airframe to handle at low speeds. He rolled in on final, everyone on board died. Pilatus is not an LSA, but it's not that much bigger either. I would advise caution.

drseti · Joined: 28 Nov 2009 Posts: 1390 Location: Lock Haven PA

FWIW, my SportStar has no stall warning horn or light installed, so it's surely not a required item on my equipment list. What it has as a stall warning is a very pronounced buffet when approaching the stall. In order for the pilot to miss that, he or she needs to be asleep.

The issue about the light pilot has to do with what happens to the cg as the fuel burns off. In some planes, you can be squarely in the envelope with full tanks (or partial tanks) with a light pilot, even with a full baggage compartment. Fine. Now, do the calculation again with empty tanks and you might see the cg move too far aft, out of the envelope. That's why they have a minimum pilot weight spec. If you're too light and flying solo, just strap a flight bag full of books in the other seat, and the problem goes away.

As for the empty tank, I'd be less concerned about the lateral balance than about why the tank couldn't be fueled. They probably resealed it, and need to wait for the sealant to cure. Everything flexes in flight -- might that flexing prevent proper curing, or result in gaps of cracks that might lead to leaks? I recently had to comply with a mandatory service bulletin that included using Loctite 648 adhesive. The spec sheet says that takes 72 hours to cure. Sure, I could have taken my chances and flown the plane before that 72 hours had elapsed, but if that negates the repair, it's false economy.

One other thing: my AOI says takeoffs and landings are to be made from the left tank. The reason for this is that the fuel pumps (mechanical and electric) provide more fuel flow than the Bing carburettors require (this is actually a good thing). An overflow circuit takes the extra fuel back into the left tank. If it were full, and you took off from the right tank, the extra fuel would be piped into a tank that's already full, and would end up either over-pressuring the tank or leaking out the vent line. If we take off from the left tank (and, conversely, land from it -- since every landing is just a setup for a possible to-around), you don't ever have to worry about over-filling the left tank. Now, with a system like this, if you seal the left tank, leave it empty, and fly off the right tank, how long is it going to be before some of the fuel ends up in the left tank anyway? My point is, the mechanic may have reasons for prohibiting flight, of which the flight instructor is unaware. IMHO, if there's a potential problem, it's the responsibility of the mechanic to ground the plane until it's flyable.

zdc · Guest

Having one tank empty on an LSA would not be anymore difficult to handle than having one seat empty.

drseti · Posted: Mon Aug 29, 2011 12:35 pm Post subject:

zdc wrote: Having one tank empty on an LSA would not be anymore difficult to handle than having one seat empty.

Conceivably more difficult, depending on where the fuel tank is installed. If the tanks are inboard, near the wing root, should not be an issue. On planes where the fuel is stored further outboard, it could become more difficult to control. The extreme case is aircraft with tip tanks. If one is full, the other is empty, and there's very little fuel in the mains, lateral stability can be compromised. That's why planes with multiple tanks and complicated fuel systems have equally complicated procedures for the order in which you burn fuel off the various tanks.

Jack Tyler · Posted: Mon Aug 29, 2011 12:53 pm Post subject:

Paul, thanks for the thoughtful answers. More than meets the eye, was my reaction.

zdc · Guest

drseti wrote: zdc wrote: Having one tank empty on an LSA would not be anymore difficult to handle than having one seat empty.

Conceivably more difficult, depending on where the fuel tank is installed. If the tanks are inboard, near the wing root, should not be an issue. On planes where the fuel is stored further outboard, it could become more difficult to control. The extreme case is aircraft with tip tanks. If one is full, the other is empty, and there's very little fuel in the mains, lateral stability can be compromised. That's why planes with multiple tanks and complicated fuel systems have equally complicated procedures for the order in which you burn fuel off the various tanks.

I said an LSA. What LSA has fuel tanks located near the wing tips? Every LSA POH I have seen so far, you calculate weight and balance on total fuel, not seperate calculations for each tank.

drseti · Posted: Mon Aug 29, 2011 4:19 pm Post subject:

True, S-LSAs have pretty simple fuel systems. Sport-pilot eligible experimental aircraft (E-ABs) can be another matter altogether. Some homebuilts have pretty bizarre fuel systems. And a lot of the sport pilot eligible certified acft (antiques) have multiple fuel tanks (wing tanks, fuselage tanks, and header tanks) that require some pretty involved wt/bal computations. Since folks on this forum may well fly such acft, it bears mentioning.

FastEddieB

flyingeyes wrote: The instructor decided to fill the other side full and do some training with a fairly new student....

This is a tough one.

On the one hand, you need to place some level of trust in your instructors, and not question every little decision.

On the other hand, its your life and safety in question, so you should question things that don't seem right.

I think its more than likely that this was a safe flight to make, yet to make flights with known deficiencies can be the first step in a chain leading to an accident. Ask yourself, in this case, what would be "The Most Conservative Action"? I'd say it would be to wait until the tank had cured to fly the plane.

As an aside, this is from a Cirrus SR22 Manual:

Note the maximum fuel imbalance of 10 gals. Its been speculated that its there because of an autopilot limit, but my point is that there may be limits or problems with an unbalanced fuel load.

Quote: If the stall horn is placarded due to malfunction is that something of concern when training a student?

Depends. I've owned two Citabrias, neither of which had a stall warning horn. I used them both for instructing, and it was never a problem.

But again referring to the Cirrus, the "Limitations" section requires a working stall warning system (see the last line here). It would be illegal to fly a Cirrus with the stall warning system inoperative.

You should look and see if there's a similar "Kinds of Operation Equipment List" for your plane, and if the stall warning system is listed. If it is, then no horn, no fly. I don't think you can just "placard away" required equipment. (edited to add: I found an Evektor manual online and don't see the stall warning system as a required item.)

Quote: Last question, if a student weighs 100 lbs and the POH says a solo pilot must weigh 120 lbs is there any concern when that 100 lb student solos?

If that is in fact a "Limitation", then I'd say no 100 lb person can ever solo the plane. I don't think even strapping on 20 lbs of diving weights would make it legal (though it sounds safe to me), but that depends on the wording and interpretation.

Anyway, it would be nice if every plane flying was perfect in every way. The reality is far different. Part of learning to fly is to learn what is important and what isn't. But I shudder at some of the deficiencies pilots routinely take off with - and accident reports often include some deficiency the pilot thought would "probably" be OK.

Quote: Thanks.

You're welcome.