Exceeding Limitations - GA

M

meritflyer

Well-Known Member
I had an old student call me today regarding him exceeding limitations on his B36 Turbo Bonanza that he just bought - two to be specific.

1) He exceeded the takeoff MP limitation twice for a few seconds; and

2) He forgot to retract the flaps during a takeoff and instrument approach (10 minutes of flying over Vfe with the flaps in T/O position - probably < 10 degrees).

His question to me was, does he need to get a mechanic to look at things now. I suspect that overboosting a turbo engine a few times isn't a real issue. The flaps was something I wasn't 100% sure of though.

At the airlines, if we exceeded any airspeed limitation, it was an automatic write-up and in for inspection. I am not sure if GA is as critical.

Thoughts?
 
meritflyer said:
I had an old student call me today regarding him exceeding limitations on his B36 Turbo Bonanza that he just bought - two to be specific.

1) He exceeded the takeoff MP limitation twice for a few seconds; and

2) He forgot to retract the flaps during a takeoff and instrument approach (10 minutes of flying over Vfe with the flaps in T/O position).

His question to me was, does he need to get a mechanic to look at things now. I suspect that overboosting a turbo engine a few times isn't a real issue. The flaps was something I wasn't 100% sure of though.

At the airlines, if we exceeded any airspeed limitation, it was an automatic write-up and in for inspection. I am not sure if GA is as critical.

Thoughts?
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I'd go ahead and get it inspected. Of course, writing it up could affect the value of the aircraft, but I'd rather be safe than sorry. I have seen the effects of overspeeding the flaps in a 172 - a bent flap actuator rod. So, at the least, have a look at it himself, at worst, write it up and get it inspected by an A&P
 
cencal83406 said:
I'd go ahead and get it inspected. Of course, writing it up could affect the value of the aircraft, but I'd rather be safe than sorry. I have seen the effects of overspeeding the flaps in a 172 - a bent flap actuator rod. So, at the least, have a look at it himself, at worst, write it up and get it inspected by an A&P
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Nothing says that it has to be an "official" inspection. Take it to a mechanic, and if he thinks he needs to tear into the plane, then things start going into log books. But a visual inspection shoulden't require any entries. Or the loog books could state simply "Inspect flap mechinism, perform engine inspection w/bore scope. No adjustments necessary @ this time." The thing is, if he did damage, the value is lost either way.


Oh, and go out and do some remedial with your student, please!
 
mshunter said:
Nothing says that it has to be an "official" inspection. Take it to a mechanic, and if he thinks he needs to tear into the plane, then things start going into log books. But a visual inspection shoulden't require any entries. Or the loog books could state simply "Inspect flap mechinism, perform engine inspection w/bore scope. No adjustments necessary @ this time." The thing is, if he did damage, the value is lost either way.


Oh, and go out and do some remedial with your student, please!
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A bore scope inspection wouldn't appear to be necessary for an over boost or two. There are safe guards in place for this to prevent damage.

I agree with the previous poster(s) that a visual should be performed.

Oh, and go do some remedial with your spell check (sorry, I couldn't resist - see bolded). :)
 
meritflyer said:
if we exceeded any airspeed limitation, it was an automatic write-up and in for inspection. I am not sure if GA is as critical.
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Vfe is evaluated as a full flap condition (or a specified setting), so it's debatable as to whether or not the pilot violated an operating limitation. And even at the full flap setting, the structure still must withstand a load factor of 2.0, so there is going to be some amount of airspeed leeway for a partial flap setting at a 1.0 load factor.

You didn't say by how much he exceeded Vfe. Twenty knots or less, I might not worry about it, but 50?
 
I'd try to find a mechanic who is familiar with that specific model. Executive Beech comes to mind right away, but they aren't cheap.

It also wouldn't hurt to step up the oil changes and do a few more frequent oil analysis. It's cheap insurance even without suspecting a problem, particularly if he does the oil changes himself.
 
meritflyer said:
A bore scope inspection wouldn't appear to be necessary for an over boost or two. There are safe guards in place for this to prevent damage.

I agree with the previous poster(s) that a visual should be performed.

Oh, and go do some remedial with your spell check (sorry, I couldn't resist - see bolded). :)
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Borescope. Overboost. Safeguards.

See what happens when you go there?
 
tgrayson said:
the structure still must withstand a load factor of 2.0
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Are you sure it is 2.0? I am unfamiliar with control surface ultimate load requirements. But structural load requirements, per USA, is 1.5. In Europe it is 2.0...?
 
tgrayson said:
Vfe is evaluated as a full flap condition (or a specified setting), so it's debatable as to whether or not the pilot violated an operating limitation. And even at the full flap setting, the structure still must withstand a load factor of 2.0, so there is going to be some amount of airspeed leeway for a partial flap setting at a 1.0 load factor.

You didn't say by how much he exceeded Vfe. Twenty knots or less, I might not worry about it, but 50?
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He said he exceeded Vfe by 20-30 knots.

The flaps were at the first notch - so not a full deflection.
 
odd, something I was thinking about today. When in the POH it says Va and Vfe and all the other speeds that have to do with structure stability and has to do with engine ops, are those speeds set in stone or does the manufacturer put in a bit of a cushion just in case you miss the speed by a few knots?
 
deek said:
odd, something I was thinking about today. When in the POH it says Va and Vfe and all the other speeds that have to do with structure stability and has to do with engine ops, are those speeds set in stone or does the manufacturer put in a bit of a cushion just in case you miss the speed by a few knots?
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As for Va, to sum up another post:

Va is square root (limit load factor) * Vs. However, the aircrafts published Va can be higher than that speed. So it can be the case where Va will be above aircraft limitations. A new speed is being introduced for that, I think tgray has the link regarding that description from the FAA. Here is the link to the past discussion: http://forums.jetcareers.com/cfi-corner/99628-certification-standards-va.html

The other speeds, I don't know, you would have to consult the certification requirements for each individual speed. I would guess there is no fudge factor built in. The fudge factor is really the difference between limit load (minor damages may occur) and ultimate load (things might rip off).

Tgray said that that this stress on flaps is 2.0 times the load limit at full flap setting. I still don't know if that is true for control surfaces as I have not seen any documentation on that. All I know is that ultimate load factors for g-limits, for certification, must withstand at least 1.5 times limit load factor, or the published g-limits for that aircraft.
 
deek said:
are those speeds set in stone or does the manufacturer put in a bit of a cushion just in case you miss the speed by a few knots?
Click to expand...

There are a variety of safety factors built in, but not always by fudging the airspeeds. It isn't possible to add a cushion factor to Va, but the cushion is built into the difference between the ultimate load factor and the load factor limit. If you're over Va a bit, you may exceed the maximum load factor limit, but not the ultimate load factor. (Assuming Va to be sqrt(n)*Vs here.)

Vne, for instance, should be .9 * Vd; the latter speed has been assured to be flutter free, so Vne provides a bit of a margin of safety over that.
 
shdw said:
As for Va, to sum up another post:

Va is square root (limit load factor) * Vs. However, the aircrafts published Va can be higher than that speed. So it can be the case where Va will be above aircraft limitations. A new speed is being introduced for that, I think tgray has the link regarding that description from the FAA. Here is the link to the past discussion: http://forums.jetcareers.com/cfi-corner/99628-certification-standards-va.html

The other speeds, I don't know, you would have to consult the certification requirements for each individual speed. I would guess there is no fudge factor built in. The fudge factor is really the difference between limit load (minor damages may occur) and ultimate load (things might rip off).

Tgray said that that this stress on flaps is 2.0 times the load limit at full flap setting. I still don't know if that is true for control surfaces as I have not seen any documentation on that. All I know is that ultimate load factors for g-limits, for certification, must withstand at least 1.5 times limit load factor, or the published g-limits for that aircraft.
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You're talking about two different things. Some poor usage of phraseology may contribute to the problem.

Tgray is correct. With the flaps extended, the airplane has to be able to withstand 2Gs without damage.

You are also correct. To be certified, the plane must withstand 1.5 times that 2Gs without failing.

There is a difference in no damage and not failing.
 
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