Propeller falls off Rex plane

[Conrad_S]

It's quieter in front. Not sure if there if there is a difference between abeam or behind.

 

[AviatorInsight]

It's quieter in front. Not sure if there if there is a difference between abeam or behind.

Really? After operating the thing for 5 years and plenty of paxing, I always found it much much quieter down the back. Rows 1 and 2 put you right next to the prop. Being on the left side for 4 of those 5 years I now have an issue in the audiogram tests whereby my left hearing is definitely worse off than the right.

 

[Quickstatus]

but it will be interesting to learn what the engine did, when suddenly unloaded.

There are 2 (propellor and turbine) speed governor in the engine linked to a control unit - in the pdf link you provided. My reading suggests an overspeed condition would cause a fuel valve divert from the turbine if the turbine speed exceed 25k rpm = approx 1500 prop rpm.
Hopefully this would prevent the turbine running rampant in a sudden no load condition or at least prevent sudden over speed giving the pilots enough time via flight deck overspeed warnings to shut it down?
Wonder if turboprop guys practice this scenario and is there a checklist for this?

 

[AviatorInsight]

There are 2 (propellor and turbine) speed governor in the engine linked to a control unit - in the pdf link you provided. My reading suggests an overspeed condition would cause a fuel valve divert from the turbine if the turbine speed exceed 25k rpm = approx 1500 prop rpm.
Hopefully this would prevent the turbine running rampant in a sudden no load condition or at least prevent sudden over speed giving the pilots enough time via flight deck overspeed warnings to shut it down?
Wonder if turboprop guys practice this scenario and is there a checklist for this?

There is an erratic torque checklist which covers a lot of overspeed, underspeed, uncommanded engine indications (like this one that presented itself) that the turboprop drivers practice for and does basically lead to an engine shutdown.

 

[Conrad_S]

Really? Clearly no point in having an opinion.

Really? After operating the thing for 5 years and plenty of paxing, I always found it much much quieter down the back. Rows 1 and 2 put you right next to the prop. Being on the left side for 4 of those 5 years I now have an issue in the audiogram tests whereby my left hearing is definitely worse off than the right.

 

[Quickstatus]

There are smartphone sound level apps. Maybe someone (JB747 may be able as he is often a pax ) can use one of these to check sound level correlated with seat position. Don't know how these apps are calibrated (if at all)

 

[Maca44]

I really don't think pax on the right side of the plane would have complained about any noise for the second half of the trip

I suspect also that with the weight loss of the prop, the pilots would have had considerable difficulty holding the plane level.
I know that they can take off/land with one engine, but with that weight loss I just think they did a great job.

 

[samh004]

I suspect also that with the weight loss of the prop, the pilots would have had considerable difficulty holding the plane level.
I know that they can take off/land with one engine, but with that weight loss I just think they did a great job.

I know some aircraft have fuel tanks in the wings and can transfer fuel between them, so perhaps they could have done that to even out the weight? Although I'm sure someone will set me straight and tell me that such a small aircraft doesn't have that capability.

 

[Melburnian1]

Really? Clearly no point in having an opinion.

Conrad_S, that's a little unfair of you to express sarcasm because Aviator Insight has always been incredibly polite to us all.

It's good to have at least three major airline pilots posting on AFF, plus others presumably in general aviation or those who have retired from military service.

 

[Quickstatus]

http://www.smartcockpit.com/docs/Saab_340B-Fuel.pdf

There is tank cross feed.
Do you want to transfer fuel over to the wing tank which just had an engine problem and possibly damage from uncntained propellor?

Without knowing the effects of a prop loss - asymmetric weight loss, drag, thrust, torque, it's really impossible to say what effect such a scenario would have on overall aircraft performance and pilot workload. Suffice to say good airmanship tend to be displayed in unusual circumstances.

There was discussion on "critical engine" in the thread about the recent Tullamarine crash. I don't know which is the critical engine on the Saab340 but with the reduced torque condition in cruise and approach to SYD, any effect from critical engine would be a less than at takeoff.

 

[AviatorInsight]

I know some aircraft have fuel tanks in the wings and can transfer fuel between them, so perhaps they could have done that to even out the weight? Although I'm sure someone will set me straight and tell me that such a small aircraft doesn't have that capability.

Quite the contrary, you're right! The Saab 340 DOES have that capability, but a fuel transfer isn't normally conducted for a weight purpose rather than a balance purpose. The rudder is more than effective at keeping the aircraft flying level, even on single engine.

Although, there was now considerably less weight, there was also now a lot less drag that a normally failed engine (even a feathered one) would produce.

They were just so lucky it didn't hit the aircraft as it sheared off, and I agree a job well done in any case!

 

[samh004]

Well there we go. I am learning things. I was halfway there. Now to work out the difference between weight and balance

 

[jb747]

The weight of the prop would be relatively trivial. It strikes me as almost the perfect engine failure...no drag from the undriven prop. Even though the thrust asymmetry looks bad, it is bread and butter for a pilot to control the aircraft in an engine out situation.

 

[opusman]

or more specifically siting adjacent to the propeller in a turbo prop.

I would have assumed the propellors rotate away from the body of the aircraft rather than towards it?

 

[gaz0303]

This accident from a few years ago may highlight the perils of row 5 - although a dash8-400 in this example
Accident: Jazz DH8D at Edmonton on Nov 6th 2014, right main gear collapse on landing, runway excursion, propeller blade(s) impacted fuselage

 

[Quickstatus]

I would have assumed the propellors rotate away from the body of the aircraft rather than towards it?

If the top of the prop rotates away from the fuselage, then the bottom of the prop rotates toward the fuselage

 

[Melburnian1]

The weight of the prop would be relatively trivial....

Apologies for behaving like a former PM (Kevin Rudd) but I eventually found what may be an answer to my above question. The wight of a propeller on a turboprop may be between 65 and 75 kilograms. Not something I'd want hurtling through my house roof at 200 kilometres an hour but then again, it's not a part of the aircraft that weights 500 kilograms.

 

[opusman]

If the top of the prop rotates away from the fuselage, then the bottom of the prop rotates toward the fuselage

Of course, but the force would be directed outwards in the event of sudden detachment.

 

[RooFlyer]

Of course, but the force would be directed outwards in the event of sudden detachment.

Which force? The rotation moment would be (I'm guessing) pretty much the same through the 360 degrees. The main force on a detached prop would be, I think, initially forwards and then backwards, either up or under the wing with the onrushing air from the forward movement of the plane. Which way it moved in the air while going backwards I reckon would be determined by the position of very last point of attachment.

I was interested to hear in an Air Crash Investigation episode that a B747 was designed such that if an engine became detached, it was designed to go forward, then flip over or under the wing (I can't remember which) and avoid the wing, tail and fuselage.

 

[Quickstatus]

A bit of trivia:
The Hamilton 4 blade propellor on the Saabs are 3.35m diameter. At 1000 rpm the rotational velocity of the tips would be
3.35 x 3.14159 x 1000/60 = 175 m/s (approx Mach 0.5 at their typical altitudes)

In comparison jet engine turbofans typically have a rotational speed of Mach 1.5 at the tips (> 550m/s at altitude)

The propellor being a high drag object (because they are designed genes to move air) might have a vertical terminal velocity lower than that of a skydiver with no parachute which is typically 200km/hr