PIREP - So much for the Cirrus

Guest Discussion
41

“THEN, when the airplane warned him, through poor performance, redlined temps, and out-of-limits annunciators, he elected to continue the flight to the original destination instead of going to his then-declared alternate and having the plane checked for possible mechanical problems! Can anyone say “Part 91.13 violation”?”

Ahem. Perhaps you’d care to reread my original post. My
original journey was LAS-GCN. I returned to LAS after this
incident, less than 10 mins out. I considered a
precautionary landing at Boulder City but, once I saw the
temps coming down, I rejected it because I was not sure of
a takeoff from a 4800’ runway. How exactly could this be
a 91.13 violation?

John
42

Jim Fallows certainly does write well (and makes me wish I could write as clearly and compellingly).
For a recent example of Jim’s aviation-related writing, take a look at his June 2002 article from The Atlantic Monthly, http://www.theatlantic.com/issues/2002/06/fallows.htm"Uncle Sam Buys an Airplane," in which he details the evolution of the USAF/USN/USMC/RAF/RN Joint Strike Fighter program.

43

The point about tending to underestimate weight and overestimate performance is right on. In my mountain flying training a huge emphasis is made on weight. There is a tendency to focus on temperature and altitude, because the POH tables lend themselves to this comparison. In fact, weight is typically a far greater factor in performance. Four “standard” people in a SR20 with 30 gals of fuel, as mentioned by the original poster, leaves 30 lbs. for baggage to be at gross weight. (Of course, I don’t know any “standard” people so who knows for sure what his weight was…he didn’t say.)

44

It such a good read. I must subscribe.

45

Thanks to the posters above for these kind words. It’s probably better, all things considered, that I try to make my living as a writer rather than as, say, a flight instructor. (Chris Baker, a one-time Cirrus instructor who gave me my instrument training in Seattle three years ago, will be saying, “No kidding!”) It’s also true that my posting things here is a sure sign that I’m avoiding doing “work” writing, as I am at the moment with a huge Atlantic piece on Iraq for the November issue.

To the main point: the Atlantic Monthly is not simply the oldest magazine in the United States, nor currently the hottest one (as measured by National Magazine Awards, newsstand-sale increases, general buzz), nor one of the two “great” magazines (with the New Yorker). It’s also an unbelievable bargain. Less than $20 a year, on an offer that includes William Langeweische’s incredible three-part series from inside the World Trade Center demolition crew. (Click here for the subscription site.) . Yes, I know this kind of pitch is supposed to go in “Marketplace,” but any of you who try the magazine will end up forgiving me this one-time lapse. And the Langewiesche articles – yes, he is Wolfgang’s son – provide the fig-leaf connection to the aviation world.

46

Andy,

I agree with both you and Bill! No flames here.

Cheers,
Roger

47

There is no entry in the SR20 POH Takeoff Distance charts for 2200 ft. press alt. and 43C temp.

Actually there is. 2200 ft at 43C is a density altitude of 5789 feet. If you look under the entry for 6000 at ISA you will find a takeoff roll of 1473 feet. The temperature/pressure altitudes are just a convenience so you don’t have to calculate density altitude. This is one of the few Cirrus performance tables were they managed to do the calculations properly. If you find an entry calculate the density altitude and look under the column for ISA at that altitude you will find the same figure.

48

I think I have to reply to this since failing to do so could be construed as concurring with the accusation of being
in violation of FARs, which is clearly not a good thing to do.
The POH does not say that takeoff at >40C is not authorized, and in fact the note ending “use extreme caution” implies
that this is possible. I’m not sure what counts as “using extreme caution”, but using a 9765’ runway seems pretty cautious to me. (Actually more than that since I started
at the physical runway end, not the threshold). Density altitude was well within the published figures, as a later post states.

I do not see any basis for asserting violation of FARs here.

John
49

Under “normal” conditions, you are of course, correct. Me Culpa. However, on reflection, the original poster did not give press. alt., he only gave true alt. and temp., so calculating d. alt. with the data supplied (missing baro. press.) is not possible.

It is still not appropriate to convert to d.alt. to obtain performance numbers in this case, since the tabulated data were taken from actual flight tests, not performance engineering calculations. That’s why the POH specifically warns you regarding temps in excess of those published.

In fact, my Denalt performance computer calculates the takeoff run at 2200 ft. press. alt. and 43C to be 2.1X of the SL takeoff run at ISA, or 3037 ft. (assuming we use the gross wt. table instead of the 2500 lbs table as you did - the original pilot reported being approx. 100 lbs under gross, not 500 lbs under gross). This is significantly different than the 2329 ft. takeoff run listed in the same table for a 6000 ft ISA takeoff run, and approaching the actual takeoff run distance the original pilot experienced. So, which is right:

(1) The Cirrus SR20 POH, which says all bets are off above the max temp entry for any line in the table?
(2) You, who rightly reminds me that you can convert any press. alt.-temp. combination to an ISA value?
(3) The FAA/NASA/Air Force, who came up with the Denalt performance computer’s equations?

Inquiring minds want to know… [:)]

My opinion? The FAA says the POH is the final word on performance and limitations. The POH specifically states any temps above 40C require caution, not conversion to ISA at another altitude. With the Denalt computer’s results to back me up, I decide conversion to ISA to get a # I want to see so I can ignore the POH warning is equivalent to using a match to illuminate the gas tank when checking the fuel level… You might get away with it, but if it blows up in your face, you’ve got no one to blame but yourself.

P.S. Get your own Denalt performance computer! They’re available through the U.S. Govt. Printing Office, and come in two versions - one for fixed pitch props and one for variable pitch props. (They’re decidedly low tech, just a circular slide rule gizmo like your old E6B.)

50

I hesitate to make this point, because of the appearance (and perhaps reality) of piling-on, but nonetheless I will:
Read in strict chronological order, from first to last posting (rather than topic-wise, by sub-threads), this discussion offers a fascinating psychological document and may actually be useful to someone profiling pilot attitudes.
We start with a broadside of the sort nearly everyone has written at one time or another: I had a problem, this plane doesn’t work, what kind of company is this, and so on.
The next half-dozen postings are all in conciliatory mode – largely, I bet, because of the “Copa Member” flag. “Sorry you had a problem.” “Yeah, the SR20 doesn’t handle those circumstances too well.” “You should think about the 22, which is much better for climbing in the heat” etc.
Then the original poster makes his first re-appearance, in full defensive posture: Why shouldn’t I have tried this mission? After all, it was blessed by the POH! Isn’t the POH supposed to be reliable? Does the company even do a bad job with its POH figures?
Then, again more or less civilly: well, actually it’s not in the POH. And anyway we (your fellow COPAns) are trying to suggest that the 20 is really pushing its luck in these circumstances, but don’t hold that against the 22 etc. And 43C is pretty hot!
Then, well it’s not “technically” in the POH, but it should be, and then on and on… until the original poster simply withdraws, no doubt fuming about the group-think mindset of the Cirrus crowd.
It is interesting to speculate how this would have evolved with a first return appearance by the poster saying, “Yeah, I’ve only taken the one trip in a Cirrus, and I’ve only been in the flying business a brief while anyway, there is always more to learn about this activity – glad to have finished this particular learning experience with no consequence more serious than a little frustration and embarrassment in front of my passengers. Thanks for letting me know what’s good and bad about the different models of the plane.” It is hard for me to imagine that as a new pilot, with one trip in a certain airplane under my belt, I would be in the “I’m certainly right, you all must be wrong” stance relative to people who collectively had made thousands of trips in the same airplane.

Again, I hesitate to raise this, because I wish no ill to anyone involved in this discussion. (Note my forelock-tugging “Friendly question” subject lines!) But I think the evolution of this discussion is a useful reminder to all involved in aviation about the temptation to dig oneself into a position, for normal human defensiveness-and-pride reasons, and the potential costs when dealing with machines that don’t care about our pride.

51

230+130+140+150 = 650, 30 lbs below 4 “standard people”.
I have a spreadsheet (very nice BTW, not done by me, and can be adapted for any small plane) that handles all this stuff,
and it took a lot of juggling to figure out what I could do. We
were close to gross but not over it (I’d weighed the baggage
piece by piece).

John
52

It is still not appropriate to convert to d.alt. to obtain performance numbers in this case, since the tabulated data were taken from actual flight tests, not performance engineering calculations.

Quoting from the POH “Computed performance data in this section are based upon data derived from actual flight testing”. These figure are calculated from flight tests made under a limited number of conditions (they did not find every possible temperature and every possible altitude to do takeoffs and landings in.

53

I agree, the C172 airframe with 180-195 hp (Superhawk conversion or Hawk XP, respectively) is the “172” Cessna should have made in the first place. For its type and era, it was a very good package.

54

It is always good to have the facts[:)]. Thanks for posting them. It seems tha the 172 XP has an advantage in Take-off and landing distances and stall speeds, and a lesser one in payload. The Cirrus has a big lead in speed and range. The factor being considered most in the original post, rate of climb, seems to be a push.

However, I think you missed an important one: Price. How much is the difference in price?

Of course, after that big number, how about cabin width, visibility, and comfort to include some less tangible factors. Lastly there is the Parachute, which everyone has their own opinions of, and the certification standards, which Cirrus had to meet a substantially higher standard.

The real point I think you’re making is that comparing the SR20 to the C-172XP would be a more reasonable comparison than the SR20 to the C-182. Other than that, the planes suit different missions, and choose according to your needs, wants and budget.

Marty

55

Roger:
I currently fly 2 Hawk XP’s in the flying club I am in. Many have a variety of conversions and your’s has the biggest engine I have seen. Most are 180-185hp 4 cylinder conversions which is what I have flown.
The biggest difference, as your performance charts show, is in speed and range. The SR20 will get you where you are going a lot faster. I have taken several hps in the Hawk behind an SR20 for ferry purposes. When we both take off at the same time time, the SR20 is at destination only 50 miles away about 10-12 minutes faster.
Your charts show payload but they do not show the fact that the room inside the SR20 is greater, the baggage compartment is larger and, of course, the avionics are superior in the SR20. In addition, there is more redundant systems such as dual vacuum pumps etc. The new Hawks are the Cessna 172 XP and their cost is in the same range as the SR20 “A” version.
If I were looking for new, the SR20 is a better value I think for all of the above reasons.
Brian

56

I agree, the C172 airframe with 180-195 hp (Superhawk conversion or Hawk XP, respectively) is the “172” Cessna should have made in the first place.

Hi Kevin,

I do wonder why Cessna is making a 180-hp 172 (the 172SP) but not a 195-hp model. Then again, such a model might be seen as competition with the 182… which, as I recall, was one of the reasons why the Hawk XP was discontinued.

But as I say, I’m sticking with our SR20.

Cheers,
Roger

57

Price. How much is the difference in price?
Marty,
That’s easy: There is no price for a new Hawk XP, because you can’t buy one. (Cessna stopped making them 20 years ago.)
The closest thing that Cessna makes today is the Cessna Skyhawk SP (not XP), which has a 180-hp Lycoming IO-360-L2A and a fixed-pitch prop. It’s not really comparable to the Hawk XP, and definitely not comparable to the SR20.
I agree with you 100% about the immensely superior appointments, avionics, and safety features of the SR20.
The real point I think you’re making is that comparing the SR20 to the C-172XP would be a more reasonable comparison than the SR20 to the C-182. Other than that, the planes suit different missions, and choose according to your needs, wants and budget.

Indeed. I could not have said it better myself. You pays your money and you takes your choice.

Cheers,
Roger

58

Brian,
I agree with you 100% about the many benefits of the SR20! I’m a full-blooded Cirrus enthusiast and evangelist, and my purpose was simply to show the difference between two different airframes with essentially the same powerplant.
The differences in takeoff distance, cruise performance, and and landing distance hold no surprises based on the different wing loadings. What really impresses me about the SR20’s design is that the climb performance is so good given the relatively high power loading. We really have learned something about aerodynamics in the past half-century!

It goes without saying that the SR20 is dramatically more comfortable and has far superior avionics than either old or new Cessnas. And I agree about the parachute (in click heremy earlier posting, see the rather puckish entry for the Hawk XP under “Maximum demonstrated parachute deployment speed”).

A couple of points of clarification:

[]The Hawk XP (model R172K) was built by Cessna from 1978 until about 1982, and was delivered with the 6-cylinder Continental. (It was based on the Reims Rocket, a version developed by the French division of Cessna that had a 210-hp Continental IO-360. The engine was derated for the US market so that the aircraft could qualify for lower insurance rates.)[]The 4-cylinder conversions you’ve flown are just that: they were originally delivered by Cessna with 150-hp or 160-hp Lycoming O-320 engines, then modified with larger-horsepower engines in the aftermarket.The current-production “upgraded” 172 is the http://skyhawksp.cessna.com/Cessna Skyhawk SP (not XP), which has a 180-hp Lycoming IO-360-L2A and a fixed-pitch prop. It’s not really comparable to the Hawk XP, and definitely not comparable to the SR20. Cessna hasn’t made the Hawk XP (model R172K) for 20 years.[/list]Cheers,
Roger

59

Amen

60

Just to prove that I’m not retiring wounded here…

I don’t think I ever said “I’m certainly right”. It’s true that 43C
is outside the figures in the POH, although the corresponding
density altitude isn’t. Actually I just looked in all the POHs I
have (SR20, 182S, 182Q, 172, 172RG) and none of them go
above 40C. Don’t know if the books for the big iron do, but
I’d bet most small planes taking off from LAS that day were
above the highest temp shown in their POH.

I certainly accept that (a) this mission was at the upper
limits of the SR20, and that continuing it as planned to even
higher airports would have been a bad idea - which is why
I didn’t do it, and (b) based on what people say, none of this
applies to the SR22.

The SR20 really seems to have the mixed blessing of superb
aerodynamic efficiency, which means it goes very fast for the power. But climbing is about very basic physics, and
200HP for 3000lbs just isn’t very much - not a criticism at all,
just something to be aware of.

My (admittedly provocative) title really referred to this particular Cirrus, and my own requirements. OTOH you Cirrus
owners are certainly a sensitive bunch, accusing people of
FAR violations (without basis in fact) just because they say
something you don’t like about the airplane you’ve chosen.

(Fortunately, if I do in the end decide to buy an SR22 - and I have to say there is nothing that measures up to it at a comparable price - AFAIK Cirrus will only look at my check and will not ask for unanimous blessing from COPA members).

John