Needless steep departures

[chrisbl]

Could be being done as a deliberate policy of a non predictable departure path to make a hostile attack less successful.


The OP is in Canada and I suspect that all areas of the government / military will be on alert and have been for some time.

[9 lives]

I have considered the "need" for this type of departure for the aircraft I witnessed. To answer a couple of valid thoughts, this was a German government non military aircraft (so zero reason for practicing "tactical" departures), and the departure runway German airport, over the ocean deaparture, has no noise abatement procedure. This guy was just playing around.

A rather subtle distinction with single engine aircraft forced approach gliding is the relationship between "best glide" speed, and a suitable speed for gliding for the purpose of actually flaring for a successful landing. Pilots may find to their horror that being high in the sky with inadequate airspeed will require trading a lot of that altitude to accelerate to a survivable glide speed. I can "glide" a Cessna Caravan at 65 KIAS, but landing at that speed would result in damage. The manual specifies an 87 knot speed after becoming airborne. This is not to achieve the most dramatic departure, but rather to assure that once that speed is achieved, the aircraft can be successfully landed ahead, if that speed is maintained. I've done the testing - 'closest I even came to thinking I was about to wreck a plane when entering a flare, attempting this at 80 and 75 KIAS.

I have no interest in having lots of altitude after takeoff, if doing so places me well below an airspeed from which a safe gliding forced approach could be entered.

As for the increased risk of the engine stopping, 17 degree pitch up sustained in a Cessna 180, is enough to cause the engine to stop for fuel exhaustion. I've done that testing too.

I have seen and learned why not to do F-18 reheat departures in GA aircraft...

[Radix]

............

[x933]

My current share-o-plane (C42 with a climb prop) goes up like a rocket when lightly loaded. Might look steep - certainly feels steep - but unless you point it at the sky the speed rockets through the white arc if you're not paying attention.

A steep climb is seldom going to end in much trouble in most aircraft - checking forward at the buffet until the speed starts coming up is pretty simple flying. It's those that hang it on the prop then start a turn that make me pucker. High angle of bank, questionable balance in the turn, and how many people are completely au-fait with the spin performance of their aircraft? I'm not in any of the powered aircraft I fly with any degree of currency.

But it looks cool, and chicks dig cool, yeah?

[UV]

Might look steep - certainly feels steep - but unless you point it at the sky the speed rockets through the white arc if you're not paying attention.

so?...take off flapless.

[9 lives]

A steep climb is seldom going to end in much trouble in most aircraft

.... As long as all engines keep running, seldom indeed. But, is it worth the risk?

Once you are higher than 700 to 1000 AGL, and flying faster than "best glide speed", all is well. But until that point, you could be playing with fire if the engine stops. Yes, most 100 series Cessnas can drag themselves up at 55 knots. They'd like to be glided (glid?) at 65 or so knots. But really, if you're planning a successful landing under stressful circumstances and less than ideal surroundings, a glide of 75 knots might leave you that bit of extra you would really like to have to flare and land - particularly if your forced landing technique is out of practice a bit.

So, if, for the sake of argument, we accept that a climb at 55 knots is possible and a glide of 75 knots is a nice to have, what's it going to take to get from one to the other if the engine snaps to zero thrust in the climb - and it has happened to me. It's going to take an alarming amount of altitude - hundreds of feet - to recover the stall you're going to have with that sudden loss of power in that attitude, thereafter to glide accelerate to the desired 75 knots. You very well may be at the ground before you have accomplished that. And, if that happens, you have arrived at the ground in a barely flying plane, with no reserve of inertia with which to arrest your high descent rate.

The associated discussions of Vmca are a bit beyond the scope of this discussion, but equally alarming.

I did formal flight testing in a Caravan, with the intention of reducing the POH after takeoff climb speed fro 87 KIAS to 80 KIAS. The requirement was to get to 50AGL at takeoff power and the stated "climb" speed, and snap the power to idle. This was the most alarming testing I have ever done in terms of I might wreck a plane in a few seconds - there was just nothing left to flare with, and I could not stop it going down.

So those who think these cool tactical departures in the C 172/PA 28 are okay to fly, take it way up high one day, and (with due respect for shock cooling) reduce the power to idle from a steep climb, and see how far you've fallen, before you can actually accelerate to a speed from which you can flare....

Now, I am delighted to have cheated death all those decades, managing to glide in two EFATO's successfully, and just fly regular departures for the rest of my career....

[chevvron]

During my PPL course, I was taught the following procedure for a short field takeoff. (Cessna 150F built in France).
Flap 10 deg, brakes on, full throttle.
Release brakes, rotate at 42 mph, climb at 50 mph until clear of obstructions, then lower the nose, let speed build up to 65 mph and retract flaps.
It's frightening the first time you do it, but a necessary part of training and you soon get used to it.

[Rod1]

The OP said "an aircraft takeoff from a runway with lots of room, and no obstacles. Just after leaving the ground, he pulled up logarithmically, and climb steeply until the inevitable point where the nose had to be lowered very noticeably. "

I suspect he would say that about my standard takeoff. Lets have a look why, consider the alternative and perhaps some other interesting points. The numbers are specific to my aircraft but I suspect the view from the ground would be similar in many modern similarly equipped aircraft.

The aircraft is equipped with slotted electric flaps with a limiting speed of 84kn and it has an electric CS prop which is set to auto for takeoff. T/O flap is 17.5deg and the stall speed in this configuration is 47kn. Max power is limited to 5 min. Normal approach is 60kn with full flap (stall 42kn).

Ground roll on short dry grass will be just under 200m, acceleration will be brisk. I will hold her down for a second in ground effect (just like a cable launch) then rotate into a very steep climb at 80kn - just over 1700fpm. We are now 4 kn under the flap limiting speed and well above stall speed. View from the ground is of a very steep climb angle (for an SEP).

It will soon be time to ditch the t/o flap. The slotted flaps will spill a lot of lift at this point and the view from the ground is quite odd - you can almost see the op shaking his head. As the flaps come up the stall speed rises to 52kn but along with losing lift we are losing drag and the prop is still in auto, the result is very rapid acceleration and as the airspeed passes 90kn it is time to rotate again and maintain 100kn and 1000pfm. The angle will again look steep but not as extreme as it did with t/o flap.

The aircraft has relatively little inertia. I have run quite a few tests at altitude and practice from time to time. The OP says you will lose a lot of height but this is not the case. With the aircraft set up with t/o flap and 80kn the guy in the right hand seat closes the throttle (stops me cheating). The nose is lowered immediately to the best glide angle, the speed stabilizes at 70kn and you go from there. The response has to be around the same timing as on a cable brake but not as aggressive. If the response is delayed the speed bleeds quickly and you have to lower the nose well past the optimum angel but you have to start pulling out almost immediately or you will exceed flap limiting speed. Hight loss is still quite small.

The same drill done clean at 100kn allows a delayed response with the angle set to give 75kn. As a slight aside if the engine stops in straight and level flight the nose can be raised till the speed bleeds back to 85kn then lowered to give 75kn, this manoeuvre will give a gain in height of over 500ft!

It is of course possible to do a much more conventional looking takoff. I sometime do a formation takeoff with some friends in there Luscombe aircraft. I let the other aircraft get moving first then apply a burst of power to get airborne then throttle right back and slot in. I am now sat at 65kn doing 350fpm and the trees look a lot bigger but the view of classic 1940's tec is worth it now and again.

Rod1

[chevvron]

I've also flown microlight Shadows with 50hp and 64hp engines. On both, you hold the stick aft of neutral until the nosewheel lifts and it unsticks at about 55kt, you then climb at 70 kts which does seem to be very steep, but it's what's recommended. If you lower the nose for a shallower climb, the speed just builds up too much. On one occasion I did a go-around at Farnborough in the Shadow D (64 hp). I opened the throttle and held it down for a few seconds, but the asi immediately leapt up to 95kt, just below max manoeuvring speed, so I rotated into the climb and allowed the speed to decay to 70 kts. The guys in the tower (the old one at the end of the runway not the present one) said they could see the entire upper surface of the aircraft and were waiting for me to pull over the top!

[9 lives]

steep climb at 80kn - just over 1700fpm

I have flown an aircraft which I believe was capable of this performance - an SM1019. I consider aircraft with such performance to be on the sideline of this discussion, though still susceptible to rather dangerous scenarios, if mishandled.

What attracted my eye, and reminded me of my disdain for this needless extreme flying was watching the German civil patrol aircraft as it climbed out. The pitchover at the top would have been a less than 1G maneuver (I've just been flying long enough that I can tell by looking). This tells me that it was more than just a lowering of the nose associated with retracting the flaps - and as the aircraft was obviously slowing as it was pitched up I severely doubt that the pilot was retracting flaps as his speed decayed. But in any case, with decaying speed there was no need to reduce pitch attitude associated with flap position, he was just doing it to prevent from fully stalling the aircraft. But yes, this was a fairly good power to weight ratio, twin engined turbine aircraft, which I suspect was lightly loaded. It was capable of a dramatic departure - but need it?

For some time here I have read responses of vigorous disapproval when someone hears that a flight was undertaken without a full walk around inspection, or someone zero G'd a PA 28 at altitude, so car keys were seen momentarily floating in the cockpit. The horror! No upward loading on the wing spar for a few moments! Yet pilots, who seem to lack the awareness of how close they are flying to a regime of flight from which recovery would not be possible in the event of an engine failure, continue to do it. Sure, if you have to get out over an obstacle, you fly the book procedure, and you do it - because, if the engine quits, you're crashing in any case!

I flew with a friend in his Bell 407 helicopter. The VSI in this really high performance machine had a yellow warning range beginning at 1700 FPM up. I asked why - who cares how fast you climb an aircraft? Bell does. They learned that from rates of climb exceeding 1700 FPM, you could not safely enter autorotation if the engine quit. You'd simply be going up so fast, that you would loose your needed rotor RPM for safe autorotation, before you could get going down to enter it. It's pretty similar for airplanes, it's just airspeed rather than rotor RPM which holds that badly needed inertia.