Challenger 604

[Atlantic-Coast]

Anyone out there with some experience on C-604.
Is this a slow cow in the climb like the Canadair regionaljet or is the corporate version
improved as far as performance.
They claim it can do FL 410 in 22 min. true or false?
Would appreaciate some posetive and negative comments on this aircraft!

Thank you

[BizJetJock]

I don't know anything about the CRJ, but here are some details about the 604.
Normal climb schedule is 250/300/.78 unless you're very heavy, when 250/280/.75. This will give you 2-3000fpm low down dropping off to around 700fpm in the mid 30's. If you need to go up quicker you can use 250/.72, but if you use that with max climb N1 the pax's drinks all fall over.
Normal cruise is .80, but you can use .82 if you're in a hurry and not worried about fuel burn or .75 for max range.
22 mins to 410? According to the performance charts, you could do that at 38,000lbs using normal climb, or 41,000 using max climb. Both are well below MTOW of 48,200. At mtow you're not going above 370 for a while, and 350 is more comfortable. We rarely go above 390 except to get above weather because the fuel economy drops off, again unless you're very light.
Generally the 604 is a very comfortable and reliable aircraft, with a useful range and good performance off short runways when it's not too heavy. The only real downside is that the handling is a bit truck-like since there's no "Q" feel system on the powered controls. If you put the effort into moving the springs, though, the response rates are quite enough to frighten most passengers and exhilerate a few

[pstaney]

Bizjet, any chance you could give me the Vref speeds for 3 weights (say 30,000 lbs, 35,000 and 40,000 lbs, or for some other suitable light, med, and heavy weights)? Then I'm interested in comparing the 601 speeds for the same 3 weights.

If I'm correct, the 604 certification was to 1.23 Vsr while the 601 was to 1.3 Vso. Since they have the same wing, interesting to see if the speeds match up.

Sorry to hijack the thread Atlantic, but I think you've got a very fine answer.

[BizJetJock]

30k - 117kts - realistic min LW
34k - 125kts
38k - 132kts - MLW

SL figures - at 10,000 38k goes up to 140kts

From memory 601 figures are generally +5kts, but I don't have the books to hand in hotel!
Hope this is useful.

BJJ

[Mad (Flt) Scientist]

Originally Posted by pstaney

If I'm correct, the 604 certification was to 1.23 Vsr while the 601 was to 1.3 Vso. Since they have the same wing, interesting to see if the speeds match up.

The same wing, but different stall protection system versions for the two types. They won't match up (in the sense that 1.23Vsr isn't 1.3Vs).

CL601 Vref, SL:
30k: 123kts
34k: 131kts
38k: 138kts

Usual caveats about unapproved data!

[pstaney]

Originally Posted by Mad (Flt) Scientist

different stall protection system versions for the two types.

Not sure I understand why/how this affects Vso and Vsr. Suppose a manufacturer designs a stall protection system to advise the pilot of an impending stall at, say, 10% over actual stall speed. Does this mean Vso and Vsr are different than if there was a 5% stall protection system?

Can you enlighten us on the difference between the 2 systems?

[Mad (Flt) Scientist]

On both Challenger 601 and 604 (and indeed 600 also) stall speed is defined by stick pusher activation - not by natural stall. Therefore the definition of Vsr/Vs is pretty much at the selection of the OEM - the more conservatively one places the stick pusher, the higher the stall speed.

Note I said stall protection - not stall warning.

So, even though the two WINGS are the same, and one would assume that the natural stall characteristics are the same, the fact that the stall is ARTIFICIALLY defined means that the stall speed can vary between types.

Add in the very different rules governing the definition of stall speed and one can easily get a very different result.

Never mind the fact that the equivalent safety assumption between Vsr and Vs is just an assumption, and need not be actual for any given type.

[pstaney]

All very interesting. I note you make a point of saying stall “protection”. For aircraft with stall protection in the form of leading edge slats that automatically deploy (if not already), is this also considered a stall protection device too, and hence the Vs speed that any multiplier (1.3 or 1.23) applies to will not be the true stall speed, but this “protection” speed?

And for an aircraft that does not have “protection”, but stall “warning” only, for example Falcon 900 with slats already extended, is the Vs considered in determining Vr or Vsr to be the actual stall then. Or is a stall tone considered protection too.

Thanks for your inputs!!!

[Mad (Flt) Scientist]

Originally Posted by pstaney

All very interesting. I note you make a point of saying stall “protection”. For aircraft with stall protection in the form of leading edge slats that automatically deploy (if not already), is this also considered a stall protection device too, and hence the Vs speed that any multiplier (1.3 or 1.23) applies to will not be the true stall speed, but this “protection” speed?
And for an aircraft that does not have “protection”, but stall “warning” only, for example Falcon 900 with slats already extended, is the Vs considered in determining Vr or Vsr to be the actual stall then. Or is a stall tone considered protection too.
Thanks for your inputs!!!

Leading edge devices really aren't stall 'protection' because they don't prevent a natural stall.

There are really two concepts in artifical systems associated with stalling: stall warning, and stall protection.

Stall warning is exactly what it says - a warning to the crew that a stall is imminent if action is not taken to recover the aircraft. Stall warning may be either natural - in the form of, say, airframe pre-stall buffet - or artifical - usually in the form of a stick shaker, and also various visual or aural cues. Stall warning does not prevent you stalling the aircraft; it just tells you what's about to happen.

Stall protection is a purely artifical means - there's no real natural equivalent. The normal form is a stick pusher, triggered by an angle-of-attack sensor of some kind, which inputs a nose-down command and prevents the angle-of-attack from reaching the natural stall angle. In purely aerodynamic terms there is no stall - no flow separation - but for certification purposes the point of pusher activation is considered equivalent to the stall, and the speed is considered the 'stall speed' for the purposes of scheduling V2 etc.

Leading slats are not considered stall protection, because they delay the onset of the natural stall, but they do not prevent the stall from occurring. The stall is therefore a "real" aerodynamic stall.

Warnings are never considered to define stall speed - the example of an aircraft with slats and a stall warning tone, but a natural stall (i.e. no stick pusher) would have the actual stall speed defined by the natural stall, and warning defined by (I expect) warning buffet in the absence of a stick shaker. I do not believe a tone, alone, would be considered adequate as stall warning (though thats not 100% definite).

Note that the Vs/Vsr nomenclature, and the associated issue of which speed multiplier applies, are strictly not related to the means of stall warning or identification in place, but were introduced in a similar timeframe to the widespread use of warning and protection systems, so there's always some confusion.

Then, of course, there's these strange aircraft from Toulouse, which don't really fit well into this traditional approach to stall characteristics ....

[pstaney]

MFS, truly a magnificient post. If I may ask 2 quick questions:
The falcon 50/900 series publish stall speeds in their AFM for clean configuration, yet it seems nearly impossible to happen since unless both hydraulic systems OR both sides of the electrical system are inop, the slats will deploy well before. So would these afm stall speeds be true clean stall speeds? Or slat deployment speeds?
You mention Toulouse, so for the A320, would it thus not use 1.23 x level speed for max permitted aoa?

[Mad (Flt) Scientist]

Originally Posted by pstaney

MFS, truly a magnificient post. If I may ask 2 quick questions:
The falcon 50/900 series publish stall speeds in their AFM for clean configuration, yet it seems nearly impossible to happen since unless both hydraulic systems OR both sides of the electrical system are inop, the slats will deploy well before. So would these afm stall speeds be true clean stall speeds? Or slat deployment speeds?

We don't have a type with auto-deployment, so I will be willing to be proven wrong here, but I would expect the stall speed data in the AFM to correspond to the approved configurations which can be selected by the flight crew. If there's no way to select a truly clean wing, then I'd expect the speeds quoted to be for the normal operations case, with the slats auto-deployed. You may be able to tell which it is based on other data in the AFM - for example, it might be possible to reverse engineer the various stall speeds from looking at the slat or flap jam/fail speed increments - if the slat failed/flap failed at zero increment on Vref is huge, yet the stall speed for 'clean' isn't so different from the normal landing config, then you might be able to deduce which it is. (Although reverse engineering from published data is always a guess, since you never know what margins the OEM has given themselves, or what other factors may apply)

I'm assuming its not possible to actually select the flaps to zero and the slats out manually - if it were there'd be a chart for that config too, which would give the game away pretty sharply.

You mention Toulouse, so for the A320, would it thus not use 1.23 x level speed for max permitted aoa?

No, it's all a bit complex for aircraft with envelope protection; my understanding (again, note the caveat) is that the max AoA speed is considered comparable to stall warning - not the actual stall - and that a speed some 5-7% lower than the max AoA speed is used as the pseudo-stall speed for purposes of scheduling the various Vsr-dependent speeds. Since industry (as usual) led the regulators by quite a bit, it'll all have been done by means of 'special conditions' and 'findings of equivalent safety' I would expect, there really aren't any rules that address the Airbus aircraft directly yet.